why 2 years in? The ps3 didn’t have ps2s install base either
Right now the big games take longer to be developed.
Specially the first ones who will take advantage of the next gen potential because means the bigge paradigm shift for game development since the jump from 2D to 3D, because they have to rebuild their engines, workflow and tools way more than in previous generation shifts.
On top of that, the rise of games as services, F2P, multiplayer and their game subscription or super cheap games made players to stay longer in PS4 specially because the next gen console is crossgen.
We also have to consider that in any generation after a couple of years a huge percentage of players still didn't migrate, and on top of that there was the chips shortage preventing new consoles being sold, so making that migration even slower. Plus also there's the past/current/future global economic crysis which makes harder for many people migrate.
Not long ago PS5 had slightly above a dozen million consoles sold, while PS4 had over 80 or 90 million monthly active consoles (not sold, active that month).
So if they spend several hundreds of millions of dollars making a game they obviously want to reach a big enough userbase to make it profitable, specially if they still didn't have the new engines and tools needed to take advantage of the next gen when like they started to make the currently released AAA games 4 or 5 (or more) years ago. Even if there are next gen only games they basically use previous gen tech with a bit of extra shiny stuff, these game could easily be crossgen specially when both generations share very similar hardware, engines and tools.