Well, in here the difference is 200€ or even more. I can get a PS4 Pro for 120€, but a PS5 with drive is around 320-350€. And for PS4 games, the difference is not very big playing in both.
You're right you can have higher framerates with less resolution, but the point is that a machine that was advertised as a 2160p gaming console in reality is a 1080p one. And no, 95% of PS4 games run at 1080p because games didn't have to deal with tons of crap like they have now, and that's the reason they are "poorly optimised" as you say. Comparing to the expected resolution of PS5, it's like most of PS4 games ran at 540p, and at that resolution 99% of them would run 60fps (performance mode equivalent). So, that mode isn't magic, it's just something PS4 base didn't have software wise.
If many games in PS4 could hit 45~60fps at 1080p, Resident Evil 2 Remake being one, now that you bring it as an example, no wonder it could hit over 100fps on PS5, I would be really worried if it didn't.
Also, I am tired of people comparing loading times between PS4 and PS5 when they don't use SSD's on a PS4. If you compare Bloodborne loading times from a PS4 (base or Pro) SSD and PS5, the difference is very little, so that's not a valid point.
You can get some info on the games here:
PS Classics Games Emulator PS1 PS2 PSP Aeterna Noctis AEW Fight Forever Agent Intercept AK-xolotl Alan Wake Remastered Alan Wake 2 Aliens Fireteam Elite Among Us Anno 1800 Apex Legends Aragami 2 Arcade Paradise Arcadegeddon Armored Core VI Fires of Rubicon The...
www.resetera.com
You will see how many PS4 games run at 1080p and how many PS5 games run at 2160p. And as an extra, you will see how little is the gain between the enhancements of PS4 Pro and PS5.
And by the way, as most of the PS5 games run ~1080p in performance mode, playing on a 1080p big TV you usually get better image quality than using a 2160p TV, even if there is FSR involved. I have tested it with a few TV's and a few games, so my premise stands, PS5 is a 1080p console, and I am not spending the 200€ difference from a PS4 Pro to a PS5, not in this gen. I prefer to save that money for PS6, where the console will be a true 2160p gaming machine, with a few games being rendered at ~1800p.
Regarding digital libraries, it can be a neverending discussion, because it depends on the person. I know tons of people who have virtually zero digital games, and tons of people who have many digital games.