I originally intended to stay out of this conversation - I've never played any of CDR's games, and don't have any particular desire to. As such, I'm not really in any position to judge whether they're "overrated" or not (a term I'm not particuarly fond of, but meh). That said, I saw their name come up repeatedly in the 'mix and match' thread, to the point that I thought "screw it, may as well get it off my chest."
Taking an outsider's perspective of CDR, there's an immediate dichotomy that comes to mind between the praise they get versus their actual products. For reference, as of 2007, they've made the following games (not including expansions/DLC):
-The Witcher
-The Witcher 2
-The Witcher Adventure Game
-The Witcher Battle Arena
-The Witcher 3
And as of this time of writing, are working on the following games:
-Gwent: The Witcher Card Game
-Cyberpunk 2077
-Untitled Witcher game
Now, I don't know about you, but there seems to be a bit of a pattern here. If you don't see it, don't worry, I know it's really obscure, but if you look close, you might just notice the little fact that every single game they've developed belongs to a single IP that isn't even theirs, that over the span of 11 years, they've never done anything outside this IP, and the one thing they're working on that isn't the Witcher is still a pre-existing IP, that's still an RPG. Hard to spot, but don't worry, it took me a long time to realize this as well.
What I've also realized is that while everyone seems to love Witcher 3, I rarely hear anyone talking about Witcher 1/2. Like, at all. I also don't hear anyone point out that Witcher Battle Arena was live from January 2015 to December 2015, that even in the crowded MOBA genre, that kind of timeframe is pretty pitiful. Now, you could say that that's a spinoff, and you'd be right, but if we're talking about the supposed "best developer evar!," I'd have thought that their resume would be a bit more...varied? Less monotonous? If you asked me what I think are the best game developers in the business, something they'd have in common is a variety of IPs and a variety of mechanics to go with them. CDR has only ever made games for one IP, in one genre (bar some spinoffs, one of which was DOA), and again, not even their own IP.
Now, none of this is inherently bad of course. You can easily make the argument that quality is preferable to quantity, and, yeah, sure, I get that. And who knows, maybe the Witcher 3 really is the best thing since sliced bread. But I'd have thought that in the realm of "greats," we'd be looking at someone with a bit more varied of a resume.