I'm no Disney apologist, but I do take issue with the notion that Avenger's Campus is a worse fit in DCA than Galaxy's Edge is for Disneyland.
As far as attractions that have been shoehorned into the California theme, tons of the additions made since opening would qualify: Bugs Land, Little Mermaid, Philharmagic, Monsters Inc...
In my opinion, the theme of a theme park serves as the connecting thread for lands that provide "jumping off points" for the various attractions they inhabit. Does Journey to the Center of the Earth or Indiana Jones have a literal connection to the Sea? No, but it works for the purpose of the theme park and flows logically. It's the same suspension of disbelief that allows us to enjoy these attractions.
Stuck with a theme like California, I think a loose interpretation of "...dreamers of the past: the native people, explorers, immigrants, aviators, entrepreneurs and entertainers who built the Golden State. ...new generation of dreamers who are creating the wonders of tomorrow, from the silver screen to the computer screen, from the fertile farmlands to the far reaches of space. DCA celebrates the richness and the diversity of California... its land, its people, its spirit and, above all, the dreams that it continues to inspire."
If you truly don't mind creating stories out of something else (that makes sense,) then I'm struggling to understand why you find Marvel and California as so incompatible. In the MCU films alone Ant-man, Tony Stark, Black Panther, Captain Marvel, all have ties to the state with countless appearances in the comic universes. (Stark Expo is set in New York btw)
For a multi-park concept, I think the Worldwide Engineering Brigades (WEB) concept makes as much sense as the Society of Explorers & Adventurers (SEA.) Stark Industries HQ is in LA, so it would make sense they'd set up a campus in California. Whether the entirety of the attractions take place in California doesn't seem like an issue to me: we're in a park about the ideas & fantasies of California; California is a real, lived-in place in the MCU, so that's our jumping off place. The inclusion of Stark/Campus/WEB elements only further support alignment with California's connection to technology and innovation (not to mention the military-industrial complex).
I guess "creating stories from things that make sense" versus "pulling things out to force it in" is in the eye of the beholder, but I think under the constraints presented to them, Avenger's Campus is a good concept, unfortunately the execution doesn't seem to be done well.
As for the Collectors Tower, that one is pretty inexcusable....no arguments from me there, I really wish they'd have used the capital that went into altering what was already one of the best experiences in the park, towards building something new to actually expand DCA's capacity.