I’d disagree on the surface with CA3:Civil War being the Jump the Shark moment in the MCU, just because of the veritable size of the industry powerhouses involved and the continuity scale involved in making 40+ movies, all the way up to 2028.
It’s so far doing well on the formulaic layout, because it’s established and there’s a fan of the genre at the helm that is capable of artful meddling for the benefit of a multi-billion dollar franchise, rather than cash grab opportunism ie. Lucas. Some disagree, argue, pontificate, but it’s not that delineated. MCU’s advantage is only that the franchise is consistent and handles it’s own fatigue by interleaving genre/characters, which is unusual.
Arguably, there will be mis-fires along the way on this herculean effort of making so many average to good movies. Thor 2, The Dark World comes to mind, as it’s fun, but mindless and detracts from the characters. It necessarily introduces plot elements and MCU integral concepts, but it’s an average movie.
The challenge might indeed be maintaining interest against ennui and action movie fatigue. The feeling of being Pre-Shark, is common for TV, in which a change in writing teams, death of a character, or story arcs will plague a larger series. In TV, the ‘slump’ after a writing arc or season, often introduces meta-challenges, i.e. are the characters interesting enough to just have them play off any kind of scenario, or is it monster/villain of the week trudgery. This is often where you get episode in a bottle capstones, i.e. one part of a series arc might be put in place, but there’s no story, so there’s 30–50 minutes of banter. Age of Ultron / Civil War might have been that period, i.e. we’re not going to see that too often in the MCU except when merging the Avengers, Strange and Guardians universe(s) to each other.
Most likely, this is why a lot of the movies are moving into the buddy or hero pairings/trios/squads, because it allows for snark and banter, quirks to filter in, something that the MCU thrives on, i.e. the hero has to be somewhat human and frail, even when they’re not human. The comic origins had space and filler to explore backstory and personality, TV also has the time to fill in character personality. Movies struggle when they introduce too much backstory (Suicide Squad, BvS) and interleave too much character or not enough character into moments and scenes. Banter, self-awareness allows character driven stories rather than story driven characters or antagonists.
The next challenge will be to introduce a decent villain into the MCU but it won’t be this decade. Giving a villain character motivation means interleaving and interfering in the hero /anti-hero dynamic. Marvel probably isn’t ready to bring in too much identity tinkering given how much is tied into Infinity War and Phase 3. Hence Phase 4 bringing in side characters, morally grey and weaker motives etc.
The remaining character movies will likely be toned down, with Black Panther and Ms/Captain Marvel being possibly the more difficult characters to handle both as MCU characters and MCU Movies, i.e. keeping enough individuality and personality that they don’t turn into 2D cardboard or analogues for the DC universe versions, i.e. brooding on ethics, capes and costumes, etc.
In 2016, Doctor Strange and Ant-Man were supposed to be the Shark Jump points, and they heavily relied on their directors and main leads to pull off a small miracle in making a hokey or quirky comic book character… likeable. 2017’s Guardians of the Galaxy 2, (another) Spiderman, and Thor Ragnarok, are going to be either tolerable or average or fantastic. or a melange of all three, with different composition and tone, enough to be palatable as different for the MCU to prevent that ennui.
The challenge is in how the 2018 Inifinity war merges the Comic with Cinematic. the serial format introduces filler and backstory because there’s time. Marvel Characters, work better in a series or serial format because they were designed on that modus. 2018/2019’s Infinity War, is where things might come crashing down, and where having 20–30 “main” characters in a movie, with some perhaps being sidelined or killed, semi-permanently, is going to add problems. Integrating the Inhumans in 2019/2020 is where things will probably try to interleave the Marvel TV series which has been run in a different direction, and it might also be a contentious problem in bringing small screen action or ret-conning the TV series to the movies.
Compared to the inevitable deluge “train-wreck” of Star Wars adaptations of a ‘thin’ war movie presence, into a 9-movie saga, I have no worries at all with Marvel.
Star Wars, just needs to get a new footing that isn’t the skywalkers.
Restarting the jedi in effect (and thus, being able to retcon the Expanded Universe of books, comics, TV, fanfiction, sic) will get there, but it isn’t easy to do. The flaw, as the ‘half in the bag’ review of rogue one noted (sardonically & sarcastically, and with dark humour), is that Star Wars is finite. The war between rebels and empire is focal. once you expand that focus, there isn’t much else known to be as challenging to overcome. Moving past the Skywalker legacy will be useful to making better characters and better stories.