2019's Avengers: Infinity War, Endgame brought to a close the Infinity Saga and the journeys of some of the MCU's biggest characters, including Iron Man and Captain America. Thanos was defeated, the heroes returned, and it was a triumphant celebration of what Marvel had done up to that point.
Avengers: Endgame, right down to its title, was defined by being the concluding act of the MCU. That's what gave the film so much of its hype and expectation, and why it necessitated a 3-hour runtime, but is also what led it to being a surprisingly more poignant affair than most Marvel movies too. At the same time, though, there was plenty in that looked to the future, albeit one that, at that point, hadn't been revealed yet.
Much like Captain America: Civil War before it, Avengers: Endgame not only delivered a massive Marvel movie (from the same writers and directors, with many of the same cast ), but ensured that it was laying much of the groundwork for the next few years of the MCU, and with strands that could be built upon for years to come.
Captain America: Civil War Setup & Defined Marvel Phase 3
Captain America: Civil War was in some ways The Avengers 2.5 (though it's very much a Cap and Buck y story at heart), utilizing most of the major MCU characters who existed at that point - with Thor and Hulk as the notable exceptions - and introducing some new ones at the same time. Although the movie's driving force came, at least in part, from actions in previous movies like what came next in Marvel's Phase 3, especially with regards to the solo movies.
The divisions between the heroes would loom over the MCU until Avengers: Infinity War, when Captain America finally re-entered the fray, and the rivalry was still a motivator for the characters into Avengers: Endgame too. The presence of Spider-Man, and hints of his backstory, was used as a launchpad for not only his solo film, but for the close relationship between Peter Parker and Tony Stark. The same goes for Black Panther, who was not only introduced, but witnessed his father die, serving as setup for his own film and character's journey to truly become the Black Panther there, alongside Bucky on Wakanda, all of which helped set it up as an important location for Avengers: Infinity War. Hawkeye and Scott Lang were both placed under house arrest, which factored into Infinity War and every Marvel Phase 3 film was directly setup here, Captain America: Civil War did a lot of heavy lifting for the solo movies, team-ups, character arcs, and plot developments that followed.
Marvel Phase 4 Doesn't Have A Setup Movie
There's no obvious Phase 4 equivalent of Captain America: Civil War in of setup. In of release dates, the first movie on the slate is Doctor Strange 2 (with its multiverse) and Captain Marvel 2 (by expanding the cosmic branch) can both setup further movies, but both arrive much too late to define Phase 4 itself.
Part of the reason for this, of course, is the delay of Captain Marvel 2 can be largely cosmic, but again, it's too late for Phase 4. That means there's no immediate movie to setup what comes next.
Avengers: Endgame Already Setup Most Of Marvel Phase 4
While there's no Phase 4 movie doing the comparable legwork of Captain America: Civil War, that's not necessarily a bad thing. As established, part of the reason is because Guardians of the Galaxy 3 was pushed back, but it's also because Avengers: Endgame has already laid so much groundwork for what comes next. Most of the conversation around Endgame understandably focused on how it served as a conclusion to so many different character and story arcs, but it was also setting up a lot of what's to come. That went for Spider-Man: Far From Home, which came after and dealt with some of the more immediate fallout, but it also goes for Marvel's Phase 4.
The first movie, Black Widow, will better explore the character after her Endgame death, filling in some of the blanks to help make that a better moment. Falcon & The Winter Soldier will see Sam trying to reckon with becoming the new Captain America, and the U.S. government attempting to fill that void too. Namor is teased for an appearance in Black Panther 2; Thor could work with the Guardians of the Galaxy, and will be continuing to find himself in Love & Thunder.
That's perhaps even more heavy lifting than Captain America: Civil War did. Avengers: Endgame was the most important movie of the MCU's Infinity Saga, since it served as the capstone of that story. At the same time, Endgame is key to Marvel's Phase 4 as well, with the reverberations of it likely to be felt long into the MCU's future.
