Review papers are interesting.
Bibliometrics reveal that they are highly cited. Internal data we had at arXiv 20 years ago show they are highly read. Reading review papers is a big part of the way you go from a civilian to an expert with a PhD.
On the other hand, they fall through the cracks of the normal methods of academic evaluation.
They create a lot of value for people but they are not likely to advance your career that much as an academic, certainly not in proportion to the value they create, or at least the value they used to create.
One of the most fun things I did on the way to a PhD was writing a literature review on giant magnetoresistance for the experimentalist on my thesis committee. I went from knowing hardly anything about the topic to writing a summary that taught him a lot he didn't know. Given any random topic in any field you could task me with writing a review paper and I could go out and do a literature search and write up a summary. An expert would probably get some details right that I'd get wrong, might have some insights I'd miss, but it's actually a great job for a beginner, it will teach you the field much more effectively than reading a review paper!
How you regulate review papers is pretty tricky. If it is original research the criterion of "is it original research" is an important limit. There might already be 25 review papers on a topic, but maybe I think they all suck (they might) and I can write the 26th and explain it to people the way I wish it was explained to me.
Now you might say in the arXiv age there was not a limit on pages, but LLMs really do problematize things because they are pretty good at summarization. Send one off on the mission to write a review paper and in some ways they will do better than I do, in other ways will do worse. Plenty of people have no taste or sense of quality and they are going to miss the latter -- hypothetically people could do better as a centaur but I think usually they don't because of that.
One could make the case that LLMs make review papers obsolete since you can always ask one to write a review for you or just have conversations about the literature with them. I know I could have spend a very long time studying the literature on Heart Rate Variability and eventually made up my mind about which of the 20 or so metrics I want to build into my application and I did look at some review papers and can highlight sentences that support my decisions but I made those decisions based on a few weekends of experiments and talking to LLMs. The funny thing is that if you went to a conference and met the guy who wrote the review paper and gave them the hard question of "I can only display one on my consumer-facing HRV app, which one do I show?" they would give you that clear answer that isn't in the review paper and maybe the odds are 70-80% that it will be my answer.