To me, it felt like the MCU veered off track mid Phase 4 - probably right around NWH.
Basically, the issue post-Endgame was that a lot of the original core Avengers were gone. Tony Stark is dead. Natasha Romanoff is dead. Steve Rogers is either dead, or a frail old man. So the MCU needed a new core avengers lineup. So we basically needed a new Phase 1 - introduce a bunch of new characters and establish them for the next Avengers.
The goal of Phase 4 initially seemed to be to pass the torch/introduce new characters. Shang-Chi was just a straight-up origin story for a new superhero. The Falcon and the Winter Soldier was basically an extended, convoluted way of turning Falcon into the new Cap (even though Endgame settled it in a single scene). Hawkeye seemed constructed to retire Cliff Barton and pass the torch to Kate Bishop. Black Widow, which was clearly just a movie made to satisfy contractual requirements, introduced Yelena, who could function as the "new Widow." So you have just the start of a good team there. Eternals seemed to be kind of a failure, but the intent was clearly to introduce another ensemble team like the GOTG, who could serve as the window to the "cosmic" side of Marvel.
The thing is, Marvel couldn't commit to this. So we got more Dr. Strange, more Thor, and more Ant-Man. In isolation, I don't think any of these movies was a bad idea per se, but they all could have been structured better to either provide a better potential closure point on the characters (ala GOTG 3, or NWH) or to help explicitly pass the torch better (Cassie absolutely could have "grown" into Stature in Quantumania, for example).
I recognize part of the issue is that for various reasons, none of the planned core of the "new Avengers" back in 2019 worked out. Chadwick died of cancer. The Tom Holland Spiderman movies have been caught in some sort of contractual nightmare with Sony which has put further ones in doubt (though we'll possibly get at least one more). And Brie Larsen is apparently so jaded from her experience with toxic Marvel fans that she's considering walking away from the franchise entirely now. But there's so many blocks scattered across the playroom floor right now man. Don't ignore them, build something with them!
