Every time a sequel or a comic book movie lands on its face, someone rewrites an article about franchise/superhero fatigue. And that's been going on for over a decade.
People will show up to watch a good movie. Guardians 3 did really well. Spider-Man is the "same old stuff." This is all cherry picking examples. Movies don't do well when they're bad or the star is unappealing somehow.
Hollywood will stop making these movies when people stop paying to see them.