You have to realize that Hollywood is constantly trying to follow profitable trends, usually without taking even a modicum of effort to determine why a concept became popular in the first place. Given how ridiculous Hollywood accounting is, there's no incentive to taking things slow, doing research, and planning things out. Studios need X number of blockbusters this year making Y dollars so they have Z profits to finance all the films coming down the pipeline, as well as line the pockets of the higher-ups. Coming up with something even remotely original takes time and effort that they just don't have, so they'll shamelessly copy whatever's popular and hope that'll work. Remember the zombie trend from about a decade ago? Remember how much zombie crap there was everywhere? Seems like a simpler time, nowadays.
But since you brought it up, let's look at the MCU. Marvel had licensed out their superheros to studios like Sony and Fox beginning in the late 90's, with mixed results. Eventually, Marvel decided to start producing their own movies, but since they didn't have the rights to Spiderman, arguably their most famous hero, nor the X-Men, they took a bit of a gamble on one that was a little lesser known (not unknown, but certainly not quite as popular). It paid off, and Iron Man proved to be a big success. And then they tossed a little teaser at the end, with none other than Samuel L. Jackson hinting at more to come.
That movie codified what would become known as the Marvel Formula: introduce a hero, have them fight a bad guy (usually similar to the hero), then drop a post-credits scene teasing one or more future movies. This culminated in the first Avengers movie, bringing multiple characters and plotlines together into one big spectacle, and it worked, to the tune of $1.5 billion. Marvel (now part of Disney) had a roadmap to success: origin movies, sequels to popular characters' individual films, and capping it off with a big crossover event. Box office records were being smashed left and right, superhero movies were dominating theaters, and the MCU had become one of the biggest entertainment franchises in history.
Of course, with how big the MCU has become, it's easy to forget just how slow it started. The first phase (Iron Man to The Avengers) was six films released over four years, some years only having a single Marvel movie released. In an age when we've been seeing a new Marvel movie on average every four months, that almost seems quaint now. But it was that slow buildup that worked in its favor. Enough time passed between each entry that you were interested in seeing a new Marvel movie, and when everything came together in The Avengers, it paid off nicely, being able to see all these characters interacting with each other at once.
But Hollywood executives didn't care about that. All they saw was the giant haul of cash that Disney was raking in with every subsequent movie, and they wanted a piece of that action. So immediately, every studio looked at the properties they owned and tried to work out which they could turn into their own "cinematic universe." Fox essentially rebooted the X-Men series once the MCU started ramping up, and that was fairly successful, up until the Disney buyout, anyway. They also tried rebooting the Fantastic Four...less successfully. Warner Bros. had the DC license and took advantage of that, but that series has had its ups (Shazam! was great and Aquaman was pretty fun) and downs (rushing to get to Justice League without setting up half of the characters was pretty stupid). Universal successfully rebooted Jurassic Park with Jurassic World, then unsuccessfully tried launching a cinematic universe based on the old Universal Monsters, which flopped straight out of the gate. And of course, Disney themselves attempted to MCU-ify the Star Wars franchise, and as everyone who hangs around this thread knows, it went poorly, to say the least.
Yes, the MCU is essentially a fairly simple template that one could follow: take a known property, build it up slowly, get people invested, then deliver the big spectacle once all the pieces are ready. But nobody in Hollywood has time for any of that. That new yacht isn't gonna buy itself, y'know!
I'd write more but this is already very long. I'll close by agreeing with
@Adamska right above me: a lot of what's copied is just surface-level, slathered over an empty shell that can be marketed to as many people as possible. Pandering to the international market (especially China) has been killing movies for a long time, and I don't see it improving much anytime soon.
