Marvel’s problem wasn’t that the films got bad. They’re actually all decent films. It’s that they got greedy. Before they thought about linking all the films, they needed to make it so all the films were great standalone films. That just made it feel like we had to commit to everything and that’s just daunting. In all honesty, films like Ant-Man and The Wasp: Quantumania and Captain America: Brave New World are decent. Though the fighting scenes were subpar in the latter. They really lack fluidity. But they suffer from the now you have to see… In short they jumped the gun and it cost them.
Also Kang was a good villain. Shame they didn’t bleed him into the universe properly. Kang versus Doom would’ve been delicious.
They cut the storyline from InfinityWar/EndGame that addressed the Hulk thing and just expositioned around it.
So on top of linking things too closely, and releasing too often, they are also dropping in just general quality of writing. Which I felt was detrimental to Quantumania, as well as the obviously crunched CGI effects that have plagued Disney for a while now.