They’re waiting WAY too long to introduce the Fantastic Four.
Looking back, the way that they
In Multiverse of Madness was a huge red flag.
Reed Richards would be the perfect character to introduce in order to bring the Fantastic Four together and introduce Doom. Reed has ties to the Avengers and is the go-to guy whenever other heroes don’t know how to solve a problem in the comics. On top of that, his arch nemesis is one of the most active and impactful villains in comics.
Reed Richards is the smartest character in the Marvel Universe and could have been used more so that the audience would have a character that can explain the whole multiverse concept in a way that makes sense. If you want your story to keep an audience, that story has to have rules. Reed Richards could have explained the rules in a way the audience would understand, keeping them invested.
Through Reed, they could have eventually built up to introducing the Silver Surfer and Galactus across several movies, and even set things up for Secret Wars.
Reed Richards is a linchpin character whose actions affect the entire Marvel Universe, much like Tony Stark in phases 1-3 of the movies. Ignoring linchpin characters like the Fantastic Four to do movies/shows about Agatha Harkness and Echo instead is not a wise move on Disney’s part.