The Marvel Cinematic Universe has single-handedly transformed the film landscape of the 21st century. Sure, there were superhero movies before it and yes, major studio franchises are nothing new. But a shared-universe concept that mixed genres, defied source material conventions, and managed regularly produce quality cinema was unheard of and was a laughable prospect only fifteen years ago.
Now, the MCU is practically a money-making machine that Disney will be milking for the foreseeable future and, since it tends to include good movies and shows, audiences are pretty happy about that all things considered. But one positive element of the MCU that often goes understated is just how much it took from the comics it is based on that it then greatly improved.
Some of those improvements, like the inclusion of a soundtrack and better visuals, are built into the medium transfer from comics to film, but then there are the bold changes to Marvel's historic continuity. These have been used to fix problems from bygone eras, refresh stale or boring characters to be more interesting, or just to make better creative choices that improve the overall quality of the narrative.