um, they did that in 2009. The MCU only had Iron Man and The Incredible Hulk in their movie lineup. So no, don't go around saying it's because Disney bought Marvel, because Marvel didn't start putting out the stuff we consider bad until after Endgame. And Marvel released a lot of top notch movies in between that time. That includes-but is NOT limited to-The Avengers, Iron Man 2 & 3, Captain America: Civil War, Avengers AOU, Avengers: Infinity War, Thor...care for me to continue?
No, Marvel didn't just all of a sudden become bad because of Disney buying it, and more or less because of a little someone called Bob Chapek being a crummy af CEO of Disney.