It's more like the a definitive example of the ability for the definition of cinema to change.
At one time television wasn't thought to be able to be as serialized as it has become since there was the thought that if too much continuity existed that people would get lost and people would then lose interest, but with the ability for people to easily stream an entire show and catch up on whatever the missed out on, more shows have been able to tell longer form stories that typically were left to other mediums to do consistently.
Maybe you can look at it as just "content" as if television is nothing more than a GaaS stringing along people with a carrot on a stick, but a lot of television at least is able to argue for the validity of the format through their desire to actually tell stories in a way that discrete episodes couldn't. It's the same with movies, which franchises have always had the cynical business side to why they exist, and whether they too were more episodic or more connected, there at least typically presents an argument for revisiting the characters and world in a way that a discrete singular film wouldn't allow them to do otherwise.
You think this wouldn't be an debate since The Godfather series and Star Wars bucked trends several decades ago and made the argument that continuous story is not only appreciated by audiences, but valid storytelling in film, and now firmly accepted in film circles as "real cinema", yet here we are at a point when Marvel ventures into the same space while ramping it up to the next level, and people want to act like it's the end of real storytelling and the beginning of pandering and leading people on.
If they saw Endgame, or at least paid attention, it's clear that they really made an effort to tell an end to a story with lots of care and respect to the characters and the story they are telling, and I think if the MCU was limited by having to tell all of it's story within the confines of 2 hours and that was it, you simply couldn't do the same justice to the journey of these characters have taken. In fact, I think Endgame (like many television series, book series, manga series, and comic series) has shown how engaging cinema can be if it dared to step outside it's self imposed limits. There used to be a time when a movie could be longer than 2 hours with intermissions, so while we've firmly accepted Lord of the Rings and Star Wars as film epics and recognize the box office success and significant of historical epics like Gone with the Wind and The Ten Commandments, Marvel has been able to reimagine the film epic, not in a discrete 2 and a half to 3 hour movie like Avatar or Titanic, not just across a trilogy, not just across a two-part film, but across 22 movies with varying levels of significance.
It may take years for the film community to accept this as they eventually did with the significance of Star Wars, but the MCU is just as much a legitimate part of cinema as many films we've seen over the last century.
