They are split into 2 versions because the PS Store is integrated with the OS this time. Also, while there were some issues, they have been fixed and there shouldn't be any problems to prioritize PS5 version on PS5. Not an issue.
So you are complaining about playing PS4 games on PS5 (who would want that?) but you want to use the DS4 on PS5 games? Every time since the NES, every new console use their own new controllers. I don't see the issue. Why would you expect any different now? Because you don't want to spend money?
If PS1, PS2 classics, etc are not supported, and Sony has stated that since the announcement of the PS5, why would you expect it? and get disappointed about it? That one is your fault.
So you expect every PS5 upgrade to be free? Just because? Also, is up to developers, not Sony.
Also up to developers, not Sony.
Again, every new console since the SNES have used a new controller. Why would you expect to use a PS5 version (not BC) of a game to work with old controllers? Want to use DS4? use the PS4 version through BC. Not an issue.
Personally, I can't believe we live in an age where people complain about things that have worked perfectly for years, but somehow they are not ok with it now? Why? I get changing something that worked to something that doesn't, or remove feature that was great, or stuff like that, but the other way around and complain that something works the same way for years? That is weird.