Mainly because a lot of the problems these guys are talking about just not materilaizing within the franchise have existed since like 2012.
Too many quips? Avengers 1, Dark World and Age of Ultron were infamous for this.
Every new movie is a sequel hook? Iron Man 2 was a 3 hour trailer for the Avengers, and this series popularized post credits scenes
Bad Special Effects? Phase 1 films looked like they were cooked up in about a week because their sets were so cheap.
Bad writing/Too much bait and switch? Remember how mad fans got over Iron Man 3 with the Mandarin twist?
I think all this discourse is less about Marvel “not being good anymore” and more about people starting to unconsciously realize that mindless corporate shlock isn’t actually that gripping once you start holding it under the microscope. Like this series has been going for 16 years and hasn’t actually changed, of course you’re sick of it.
or in falcon and the winter soldier.
the “bad guys” want refugees to have rights, and the only way to convince the audience of them being evil is having them kill an american soldier on screen while the leader says “it had to be done”
and when the show comes to term with the fact that they were objectively not evil and their requeste made sense, they have falcon write a strongly worded letter to mr. local politician. you know, the REAL way to protest and achieve change.
a loooooooooooot of marvel productions follow this blueprint of “hi, i am the bad guy, i want free lunches in schools, abortion rights, and an end to racism. Oh, i also kill baby seals as a hobby”