Five years before Avengers: Endgame was released and Earth's mightiest heroes found themselves on a trip through time and the entire Marvel Cinematic Universe, another superhero movie did it first. X-Men: Days of Future Past arrived in 2014 and not only combined the main casts of its two series, but linked them up in a proper time travel adventure. The architect behind the screenplay for that film Simon Kinberg is no stranger to other franchises though and opened up about his thoughts on how Endgame used the Time Travel motif for its plot in a new interview.
"I think the MCU's tone in general, with few exceptions, is a little bit more playful than the X-Men movies," Kinberg said while appearing on IGN's latest WFH Theater commentary. "What we did with the X-Men movies was try to create something that was a little more, I guess I would almost call it 'operatic' or 'dramatic,' even bordering on 'melodramatic.' Whereas the MCU movies are largely more fun and poppy and playful, not that they don't have their serious moments too and obviously Endgame has some very serious moments, but the way they handled time travel feels to me in line with the general tonality of their movies. Whereas I think for us this fit more with the tone of what we do."
Despite Kinberg's extensive history in the X-Men franchise (writing five of the movies in total) it seems unlikely that he'll have any creative involvement with the characters when Marvel Studios eventually reboots them for the Marvel Cinematic Universe. That said, there are a whole host of uncertainties when it comes to how the X-Men will be incorporated into the MCU when the studio does eventually decide to bring them to the big screen once again.
"It'll be a while," Feige told io9 about Marvel Studios' X-Men plans in April 2019, shortly after Disney's purchase brought the X-Men, Deadpool and Fantastic Four screen rights from Fox back to the House of Ideas. "It's all just beginning and the five-year plan that we’ve been working on, we were working on before any of that was set. So really it's much more, for us, less about specifics of when and where [the X-Men will appear] right now and more just the comfort factor and how nice it is that they're home. That they're all back. But it will be a very long time."
To make things even more uncertain, Marvel's entire Phase Four slate of films have been delayed in the wake of the coronavirus pandemic, perhaps pushing back the arrival of the X-Men in the MCU even further.