The United States and the United Kingdom have world famous universities with very good reputations in various fields, such as Oxford, Harvard, MIT or Princeton. On the other hand, Ireland, which is an English-speaking developed country, has few well-known universities. It has Trinity College Dublin, but it is nowhere near as famous as its American and British counterparts. Moreover, Irish universities are ranked poorly in all university rankings, such as the QS Ranking or the Shanghai Ranking. I am very curious about this, why are Irish universities ranked poorly and are relatively unknown despite Ireland being an English-speaking country?
Caution: there are so many biases in international rankings that it's questionable whether they actually represent anything other than what people believe to be the institutions reputations.
That being said, it should be noted that it's not surprising that a country with only 5 millions inhabitants, which was one of the poorest in western Europe until the 1980s, does not rank as high as countries which have been much stronger in population and in wealth for centuries. Let's not forget that Ireland did not even exist as a country when the UK was colonizing half the world (including Ireland), and this alone could explain a little delay.
If anything, Ireland actually had an absolutely brilliant recovery in the past few decades, becoming one of the top modern economies despite its small size.
Historical reason: Ireland's population started only recently to recover from the famine of ~ 1840 and decades of emigration. The population recently made it back to the level of 1800.
It takes some time to build up "credibility" for "rankings" like QS or Shanghai ... because these ranking are purely opinion-based: they are surveys, they do not hold intrinsic value (as an example please read a critical review (Krauskopf, 2021) of Shanghai "ranking").
Krauskopf, Erwin. (2021). The Shanghai Global Ranking of Academic Subjects: Room for improvement. Profesional de la Informacion. 30. 1699-2407. 10.3145/epi.2021.jul.08.
Questions of this kind pop up on this site on a regular base and under such questions several answers and comments typically point out why such rankings tend to be heavily overinterpreted and tend to be a poor measure of the quality of education. I agree with those answers and comments - but there is another important point which is often not stressed as much and which also applies very much to the present question:
Let us, just for the sake of the argument, ignore all the issues with those ranking and assume that they do indeed carry a lot of relevant information. Then the premise of the question seems to be that the United States and the United Kingdom do extremely well in those ranking, and thus the question arises why a certain other country (in this case, the Republic of Ireland) ranks worse. However:
The premise that the United States and the United Kingdom do very well in those rankings is not supported by the results of the rankings.
For some reason people tend to look at an extremely small percentile of those ranking, see that most universities there are from the US and the UK and conclude that the US and the UK did very well on those rankings. It is, however, worthwhile to note that, for instance, the top 25 universities in the QS ranking only represent the top 1.66% of the overall about 1500 institutions that occur in those ranking - and that, in turn, those 1500 institutions only represent a small fractions of all institutions of tertiary education in the world.
So if your main interest is in those universities which rank top 2% or so in, say, the QS ranking (and even in a much smaller top fraction of all universities worldwide), then you can come to the conclusion that the US and the UK are top.
If however, you're interested in, say, the top 10% (which is arguably still very good) the situation is entirely different. For a few countries I computed the number of universities that occur in the top 150 (i.e., the top 10%) of the QS ranking linked in the OP, normalized per 10 million inhabitants. Here are the results:
Switzerland: 6.7 (6 / 9 millions)
Denmark: 5.0 (3 / 6 millions)
Sweden: 4.5 (11 / 11 millions)
Australia: 4.1 (11 / 27 millions)
Netherlands: 3.3 (6 / 18 millions)
United Kingdom: 3.2 (22 / 68 millions)
Republic of Ireland: 2.0 (1 / 5 millions)
Canada = 1.8 (7 / 40 millions)
South Korea = 1.2 (6 / 52 millions)
United States = 1.0 (34 / 333 millions)
Germany = 0.8 (7 / 84 millions)
France = 0.6 (4 / 68 millions)
So if you consider how many universities a country has in the top 10% of the QS ranking, Ireland is somewhere between the UK and the US, and the US ranks much worse than several smaller countries.
(I'm now tempted to ask the follow-up question "Why do the US lose out in university rankings?", but I think I'll rather refrain from doing so... ;-) )
Remark. My answer is related to the much shorter answer by Anonymous Physicist, but there are two differences why I think that a separate answer was warranted: (i) the other answer speaks of average universities, while the numbers that I listed above show that the same phenomenon even occurs in the top 10%; and (ii) in addition to general observations about quality and reputation of universities beyond the top few percents, it's worthwhile to point out that even the numbers in the rankings themselves show a completely different picture if one leaves the extreme top of the rankings.
New Zealand is another (primarily) anglophone country with around 5 million people, like Ireland. The top 2 QS rated unis in Ireland have scores of 64 and 49. The top 2 in NZ have scores of 68 and 45 (the latter of which is of course underrated because it's where I did my undergrad), practically indistinguishable. You could say perhaps that you'd expect Ireland to attract more talent by being close to Europe and in the EU compared to the remoteness of NZ, but otherwise I think this is just where this category of country tends to rank.
Academic ratings take different factors in account, and it is not possible to name one single reason why a University (Irish or not) is placed lower than they would have liked to.
A University essentially consists of people. Hence, the ability of the University to attract and retain high-calibre academics from all around the world is essential. So, what does attract best academics and motivate them to move to a particular place?
- How famous the place already is. The currency of academia is fame, and academics love to be associated with famous Universities just like Universities like to link their history with world-famous people (Nobel laureates, politicians, etc). Long established Universities have acquired a lot of recognition and fame over the years, so for them being high in ratings become a self-fulfilling prophecy.
- How well it pays. In many countries academic pay scales are strictly defined, but in some it's more competitive. In many countries research grants can only be used to fund research (postdocs etc), but in some PI can boost their salary from the grant. In many countries researchers are obligated to publish, but in some they are also offered financial incentives for each paper.
- What is the teaching/research/admin balance in the workload. Some Universities are predominantly research-focused, and academics are asked to teach one course per year maximum. Some are teaching-focused and academics are asked to teach 6 courses per year and do admin tasks. While research fame remains with the researcher, and is recognised nationally and internationally, the success in teaching is only appreciated within the Department. The balance is predominantly defined by University strategy, i.e. if they target fast income from teaching, or slow income from research. Academics who value their research would not consider moving to a teaching-focused University.
From what I know, Ireland had some tough times in 19th century, and most of their Universities are relatively young. Irish Universities are reasonably teaching-focused, and they offer slightly better payscale compared to the UK, but lower compared to the US or China. This may be a significant factor in why they can't quickly attract excellent researchers or retain their best staff. This in turn may affect their ratings.
As an Irishman and ex-attendee of Irish and overseas universities I might pitch in my two cents worth here.
As a minor (non-empire) country of Europe, I think we are generally in line with rankings of other similar countries, i.e. Denmark, Norway, Finland, etc.
The larger European countries all have old or 'flagship' universities that have rankings far above those of other universities in their own countries and these inevitably capture the lion's share of ranking-based attention.
My concern is that people reading rankings would foolishly assume that all departments or grad schools in a high (or low) ranked university would have equally high (or low) prestige.
You mention Trinity College, Dublin - the highest ranked Irish institution. This university does have some excellent departments but these are more notably in arts, humanities or med/life sciences rather than physical sciences or engineering. The historical reason for this relates to the limited funds available for high overhead labs and the lack of political pull exerted by Trinity versus its rival UCD - where most civil servants and politicians attended. This started to change in the 1990s when new University of Limerick's success in funding itself from overseas sources, philanthropic foundations, etc turned a few heads at Trinity and a strong fund-raising foundation was soon formed with many billionaires invited aboard. TCD's growth in physical sciences is also deterred by the confines of its mid-city campus site and unsuitable old buildings. Were a TCD Tech Campus to become a reality on another nearby site, I have no doubt it would grow much faster away from the burdens of antiquity in College Green.
The QS Rankings purport to distinguish between high and middle rank staff and likewise for research publications; and so they should. Yet I am often left with a feeling that universities with a known strong reserve of funds are weighted more than those without as much, even where their strictly academic performance may be inferior. Yes, endowment implies a capacity to buy in top-rank staff or build up expensive laboratories quickly. Yet of course with people it's usually not so much what they may do as individuals but rather what they can and will achieve as a group that counts. Ambiance really counts and no amount of money can buy a sense of how to relate well academically.
"Reputation" among academia is two things - the QS type thing and the actuality of what you and your colleagues think of University of X's graduates in Y based on your combined interaction with them as published researchers, fellow-contributors at conferences and even as PhDs or hires. To me, the latter is the true meaning of reputation as academics of different institutions talk about such things to each other. QS Rankings are far too simplistic to evaluate this.