I don't think that's really true, the quality seems the exact same as all the other previous phases to me.

The last 5 MCU films have had 3 films under 75% on RT. The entire MCU before that had 2 films. It's a trend of their films being less well received.

https://editorial.rottentomatoes.com/guide/all-marvel-cinematic-universe-movies-ranked/

Do you think Chloe Zhao, coming off the back of an Oscar win, was backed to make the best movie she could make? It felt to me like she was told exactly what type of film to make and I couldn't feel any of her personality through the movie. Compare it to a comic book movie like Joker or Logan where the creative team really were able to make good arty films.

You know when you see a Scoscese film, or a Tarantino film, you can immediately tell its their movie through the way it's shot, the dialogue, the framing. When was the last time the MCU had a film where you could see the directors input? GotG, maybe?

I don't think there is any evidence that Marvel are trying to make the best movies they can, to me it seems like they're trying to make the most profitable movies they can first and foremost.