I mean, I won't say everything is better, but it's not exactly as bad as you're saying either.
Sure, 1000s of games are bad. 1000s of games were bad in the 90s and 2000s too. Bugsby 3D was allowed to exist.
OP isn't even able to say games back in the day were good as he has already bashed N64 and Gamecube (lame move btw, Goemon's Great Adventure I still play every year). He's very much just thinking of PS2.
How many people have missed out on Hat In time exactly?
You're...just objectively wrong then. A Hat in Time was one of the best platformers released in the past 10 years, and even if you don't like it you can't base the entire genre on your own opinion.
From what i'm gathering your issue is less that the genre is bad and more that there aren't a lot of "dark, gritty, realistic" platformers...which...there never was.
Like unless PS2 somehow had literally all of them *you haven't given examples other than ratchet and clank) You got Sonic and Mario in early 3D, Banjo Kazooie and DK 64 at the peak of early 3D, conker's bad fur day which is dark but also extremely cartoony...
Then you got platformers like Okami which again...cartoony. Goemon's 3D platformers and thats all cartoon
Like I'm basically trying to say more games in the platformer genre were cartoony than not throughout 3D platformer history and we need more examples of what you really mean
But like you're basically making a claim the entire genre currently is bad over an opinion of something that was never really that common to begin with.
edit: I even tried looking up platformers on PS2 and was greeted with Sly2, Rayman (did that have a 3d platformer?), psyconauts, Spongebob: BFBB
Like great games yeah, but the thing you're basing the entire topic on really seems to be a minority if your issue is a particular art style....
Why aren't modern 3D platformers as good as the PS2 era of 3D platformers?
Please prove me wrong and suggest me some modern ones that stand up to the older ones....