I agree with your concerns, but I think the whole multiverse concept is an attempt to keep the MCU fresh and keep this superhero film gravy train going. As it is right now, the MCU was and still is an experiment that has massively paid off for Disney.
When the first Iron Man movie came out, the idea of bringing Captain America and Thor into the same universe as this new Iron Man franchise made me groan, because at that point, the general movie audience that was into superhero films were accustomed to grounded comic book movies that felt as if they could be taking place in the present day. I actually ended up skipping both Cap and Thor 1 because they didn’t fit into my own head canon for Tony Stark’s universe.
Fast forward to the Avengers, which took the Tony Stark world of modern day anti-terrorism and drove it head on into the cosmic Marvel universe, complete with an alien invasion that almost destroyed NYC.
I think this was the moment that a lot of people got on board with an expanded MCU that took its focus to the stars and a bunch of reality-shaping gem stones. We’ve seen commercially successful films featuring a talking tree and raccoon, a fictional African nation with advanced technology based on a near indestructible metal, Norse Gods made into actual extraterrestrial beings… I could go on, but knowing this, it’s hard for me to believe that a multiverse-based storyline is where audiences are going to put their foot down and say that superhero movies are no longer enjoyable.
I do think that eventually this craze will come to an end. I really can’t see what they’ll do post-Kang the Conqueror because how can you really top a multiverse… but maybe this is Marvel’s way of creating an exit point. Instead of building up to one massive event ala Infinity Gauntlet, let the remaining story threads kind of expand out on their own, left to succeed or fail without an end game in sight… and if the market justifies it, maybe an Avengers 5 or 6 will be based off a final conflict with Kang.
