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.
Probably the most egregious example. I think as well of Civil War, where the conflict that arises is literally over whether superhumans with the ability to kill billions of people should maybe perhaps have a teeny bit of government oversight. All after the Avengers have been found guilty of being responsible for the deaths of tens of thousands! IIIRC; maybe even more. People like to pretend sides were presented (and thusly make it their entire fuckin personality, a la Edward vs Jacob for Twilight), but the whole damn movie wants us to understand that Tony is a little beta cuck willing to bow down to Big Government, whereas Captain Amerikkka is our based big boy PatrioticTM libertarian. Throw Captain Marvel basically being an extended U.S. Air Force advertisement on toppa that shit pile, too.
People like to say Thanos did nothing wrong, and some of us rightfully say that Thanos should have just doubled the resources or installed multiverse-wide communism. I’m starting to wonder if Thanos isn’t literally what the writers of this garbage think of actual communists. Killing people, but for equality, and that’s bad and just like Stalin! Blegh.
tbf Thanos’s objective and the means with which he planned to achieve it never made sense regardless of the angle you look at it from