@strawberr-ily Yeah, I agree with you.
I think the reason for why they are disappearing, it because the actors have finished their 9 movie contracts and don't want to play there roles anymore. And why they introduce so many is because there are like 150 more marvel characters in the comics, and Marvel Studios want to introduce them. When they do, they bring in new actors and they sign a 9 movie/show contract.
Phase 3 is also probably my favorite, expect for a few movies in Phase 2. Phase 4 is coming to end after Black Panther Wakanda Forever, which I'm so extracted for.
Phase 5 and 6 are probably gonna be so confusing and introduce so many new characters. Like after Multiverse of Madness, they do as much as they want. If you go to Marvel.com and see upcoming movies and shows, there is soooo many things. And literally 3/4 of them are new characters.