Yea, it's definitely a lot of issues but lack of quality writing is I think key. Marvel has proven itself easily capable of hyping up unknown characters into giant blockbusters. But the writing.....yeesh.
I think there's three major things I would fix, though who knows how it would help.
1) Less stuff. Between the shows and the movies, we are getting SO much content that it's harder and harder to become invested in it. Didn't like Moon Knight? Don't worry! 2 movies and 3 other shows will be here in a few months. Giving us more meaningful movies/shows with time to really miss it might help. It also means we keep getting new characters and then having to wait years for them to do something else because they need those years to tell the stories of 30 other characters.
2) Stop leaving all of the writing to TV writers. I love Rick and Morty as much as the next nerdy 12 year old boy. I think the writing is generally brilliant....for a 22 minute show that focuses on a sense of overall meaninglessness. These are movies. They need to be written by people who truly understand how movies are written. Marvel may be one huge television show, but it doesn't actually work that way when you have 2-2.5 hour episodes and 3-5 months between each episode. So yea, move away from a TV mentality for the movies. Give us proper structures with movies focused on character and less 18 things happening to get to the other thing to get us to the last thing.
3) Get Kevin a partner. Kevin is a genius at the bigger picture, but now the picture is HUGE. I think he needs to focus on how things add up but he can get a partner or two to focus on the individual movies, make sure movie X is great as is, and also connects to storyline Y later on, but again...doesn't JUST do that.