The MCU didn’t start with the movies from Fox or Sony because Iron Man was one of the characters Marvel the company didn’t license off back when it had money problems before Disney bought it. The MCU is specifically stuff put out by Marvel Studios after the acquisition by Disney. It’s why Scarlet Witch gets her powers from the Infinity Stone and not from being Magneto’s daughter as written in the comics.

For your other comments, I agree, the studios have gotten lazy. They have gotten used to an investment of $200 MM plus another $150 MM in advertising yielding $1.25 BN in theaters for the major franchises. Even as superhero fatigue has set in from oversaturation, they still keep pushing out boring movies, with DC bring even worse than Marvel in this regard. I liked Wonder Woman, but the sequel was unwatchably bad.

There’s a problem of trying to make “safe” movies and keeping a PG-13 rating when the stakes necessary to challenge a lead character with superpowers necessitate death and destruction on a large scale. Transformers has a problem that in fights it gets really hard to track which cybernetic organism is the “good guy”, and when the fight is destroying apartment buildings, can there be a true good guy? Blade at least is killing vampires to save normies, and also steered into the R rating. There’s a lot of blood in the Blade movies, unlike pretty much everything from Marvel and DC.