There’s a very specific South Park episode that relates to this comment - “ You're Getting Old" (Season 15, Episode 7).
There's a lot of nostalgic things that do in fact suck, I have no problem admitting that. Subjectively, I will die on the hill that movies overall are getting worse though. They are all starting to feel over-produced and sanitized. Objectively, the time between seasons of hit TV shows is increasing, we can measure that as a fact. Not rose-tinted glasses.
Imo, the problem is fragmentation, as everyone doesn’t watch the same tv/movies anymore. We don’t have shared experiences of watching Lost, Breaking Bad, Game of Thrones and etc., which used to be a global phenomenon. They do pump out quality TV (e.g. some Apple originals are top notch), it’s just it’s not like that golden era anymore.
Kinda agreed with you though, but I’m also getting old, so maybe my judgement is skewed as well.
If I remember correctly Stan realized that the old things he liked were shit in that episode. Anti-nostalgia. OP describes the opposite.
I haven't seen the episode but I can imagine the critique is pretty valid. However, sometimes it goes too far in the opposite direction. Sometimes things _are_ actually worse now :)