It's not that simple. Obviously this generation if a genre benefit more from 60 FPS, 60 FPS will be there more easily. But we shouldn't look too much to the present to think it's done for 60 FPS mode in every title; if you take the PS3 remaster on PS4, all offered a 60 FPS mode. So CPU wasn't a problem neither on PS4 for the older titles. When the CPU will be pushed more too in the next future, I don't know if scale down the graphic details will be enough for a 60 FPS mode imo.
comparing remasters of games to cross gen titles it completely unfair.
look at cross gen titles on PS3/360 and PS4/One, and now look at cross gen titles from PS4/One to PS5/SX
almost no cross gen game, and not even remotely all remasters, run at 60 fps on PS4/One if they ran at 30fps on PS3/360
GTA5 still runs at 30fps, Assassin's Creed 4 still runs at 30fps, Far Cry 3 still runs at 30fps, Far Cry 4 still runs at 30fps, Assassin's Creed Ezio Collection still runs at 30fps, Sleeping Dogs... you guessed it... still runs at 30fps.
so even a shitload of remasters did not actually get am FPS boost to 60fps, and the vast majority of cross gen titles didn't either
now this gen a 30fps game is the weird outlier not the norm. Watch_Dogs Legion only is 30fps and people quickly pushed the devs to patch in a 60fps mode which they now will do. Same with the Series S version of Assassin's Creed Valhalla, they even gave that a 60fps patch
and on the note of the Series S, that system singlehandedly might be the reason we will always see 60fps modes on PS5 and Series X. because even when the Series S might miss out on a 60fps mode, you can be assured that running the same game on PS5 and Series X at the Series S settings will always result in those games running at 60fps for sure.