Posters are hard to get right. They require design skills and knowing what the core message of your paper is. Presenting them requires people skills. Aside from this, different areas seem to have different criteria and norms when it comes to this so if you want to fit in you should try to follow those.
But in general, most scientific posters I've seen are really terrible in terms of tools for communication: they have far too much text and get into far too much technical detail. For example, on this site posted in the comments on the question, there's some nice visuals but all of the posters have, in my opinion, far too much text.
One excuse for a lot of text on a poster I often hear is that people will can read them on their own between sessions or whatever. In my own area and experience, I don't buy this argument: that's what the paper is for and I rarely see anyone reading these literal walls of text in their spare time.
The advice you've gotten from the internet seems to follow that thinking: the thinking of printing a full paper on a poster in bullet form. An A0/A1 wall of text is not the best way to sell your work, nor is a boring traditional narrative of introduction, methodology, results, related work, conclusion or whatever.
I say this from the perspective of someone who's gone to too many poster sessions and gotten trapped at a poster where someone for some reason decided I would be interested in spending 20 minutes silently listening to them recite the slightly abridged version of the paper that they had for some reason decided to printed on their poster. One guy even seemed to expect me to leave after he was done. After he had finished reading the conclusions at me he had a look on his face that said "who's next?".
Okay so that's one extreme.
For me, the secret to a good poster presentation is two-fold: the poster and the person in front of it.
In terms of a poster session, people will probably have some food with them, people might even have some drinks, you should not assume to take more than 5 minutes of their time, they're probably not going to get all the technical details and they're definitely not going to read a wall of text. At least one would hope that they wouldn't read it because that would imply that you'd be talking to yourself since they cannot read text and listen to you at the same time (unless you're reading aloud the text that is).
When I was working with students on posters, I would always advise them to dispose of the idea that they can or should communicate the full technical depth of a work on a poster to a passer-by in five minutes.
Their goal should be to motivate and communicate enough of the core ideas of the work to convince people passing by their poster that the paper would be worth taking the time to read and to teach them something cool.
In terms of that goal, I would bring the student to a white-board and tell them to pretend I was a conference-goer who knew nothing of the work but we met at a coffee break and I asked them to tell me about the work. They can use the board or ... if really needed ... they can point to something in the paper. While presenting, they should appear enthusiastic (without overselling) and emphasise why the work is important ... why I should care, and what the main results were.
They should also listen to what I say ... it should be a conversation. They should make sure that the person they're talking to is following them ... that they don't just launch into a 10 minute soliloquy at the first person that looks in their direction but that there's an element of interaction.
After that exercise whatever they were trying to represent on the board or whatever they needed to point at in the paper: that and pretty much only that is what goes on the poster ... diagrams, examples, main results ... things they can point to help them explain verbally what the work is about.
Then we'd sketch out a poster and try make it visually appealing ... try to tell a visual story with it ... try to make it attractive for people to come over and ask what it's about.
Not that the end result is always perfect, but the approach does lead to a better result in terms of a communication tool than the wall-of-text approach that seems so bizarre to me in the world of scientific posters.