I have submitted a review article and one reviewer stated "Authors should propose their solution(s) in this topic based on the analysis of different literatures." So my question is: it is really required (or expected) to include suggestions on how to solve the research question tackled by a review article? I have read numerous reviews (in journals of good reputation) that were just a collection of findings from the reviewed references, with very little opinions from the authors added. To provide solutions would in my oponion require research that authors of review papers might not have done (yet). So is this reviewer right to ask for this addition to the paper, or would it be ok to decline the request (and if so, with which justification)?
You did not say what discipline you are submitting in, but in my discipline of information systems, not only is the reveiwer's request normal, but editors of the most reputable journals might even desk reject your article (that is, refuse to even send it out for review) if you do not add significant commentary beyond simply summarizing what the literature says. So, from my perspective, the reviewer's request is very reasonable.
If you do all the hard work of compiling and summarizing the literature, you should be in a good position to go beyond mere summary and actually synthesize the results to see something beyond the mere sum of what the literature says. If you would take some time to reflect on how you may do this, it would be very valuable to your readers. I believe this is what the reviewer is hoping to get from you.
I am admittedly biased in this regard: I recently wrote a working paper on this very topic with detailed tips on how to add insight beyond a mere summary of literature. If it might help you, here it is: Developing Novel and Relevant Theoretical Contributions with Literature Reviews. The gist of my ideas there is that, beyond the necessary summary of the literature, review authors should further look for contradictions or shortcomings in the literature and they should either try to resolve them or they should highlight the importance of the need for further research to resolve these contradictions or shortcomings. I give practical tips (and references to other helpful articles) that show how to do this.
I agree that the request seems odd, but I haven't read your paper. For many things no real "solution" would be possible. For others, it might be. Think about the request and see if there is something that is worth saying in the paper, but it might just be that a note to the editor that the request isn't really possible to fulfill in the current context might be enough.
It is possible that the reviewer is inexperienced, but it is also possible that the reviewer is very experienced and sees something that you haven't noticed. So, it is worth a look.