I know people give Thor: The Dark World a lot of shit, but I genuinely liked the first 15 or so minutes before they broke all pretense of caring and reverted to The Marvel Way™ of making stupid jokes every 30 seconds. Considering the trash that was Ragnarok and how most decent moments with Thor have been when they took him seriously, I think with 20/20 hindsight they should've played it straight.
I have a higher opinion of Dark World compared to most, though that might change as I see it getting a resurgence. I like that they played a majority of it straight and had some actual stakes. Would never have expected a Marvel film to kill the mother and throw a nice funeral.
Thor is the ultimate victim of the "Marvelization" of everything. What should have been a strong set of fantasy films degraded into a spiral of Thor "finding himself" while getting increasingly overtaken by irony and Marvel's obsession with Sci-Fi. Seriously, why is the big fantasy IP filled with nothing but space ships and laser guns.
When Ant-Man was teased, I thought Marvel was really scraping the bottom of the barrel , and it became a by-the-numbers thing. I guess they felt that growing/shrinking and magic was enough to differentiate the three, but different personalities would've helped. Strange has enough knowledge on otherworldly problems that it's not out of left field for him to be more serious - if he had a more serious, pragmatic personality, I think it would've worked better and had more mileage out of Cumberbatch.
They pretty much were scrapping the bottom of the barrel. Marvel's big hitters are Spider-Man and X-Men. Those two series are the only ones with their own fleshed out world, cast, rogues, etc.. Characters like Iron Man and Ant Man were built with the idea of the Avengers and wider Marvel universe carrying them. At best, they have 1-2 good villain and/or storylines to make use of without involving 20 other characters.
Iron Man was the strongest of the universe in terms of story-telling, and even he was directionless past the first. All of phase 1 was a repeat of Tony needing to take responsibility, while phase 2 and beyond were a repeat of Tony getting brain worms and deciding he needs to "end the fight," only to fuck up everything. I swear Iron Man 3, Avengers 2 and Civil War all give him the same plot. This might have worked if they had any interesting villains to add new dimensions, but every Iron Man villain sucked
Marvel can't even replicate it.
They really got lucky with Iron Man being the hit it was. RDJ as Iron Man carried the entire universe through sheer charisma. Marvel was also smart enough to drop an endpoint early with Thanos, so people felt compelled to see the story through.
They can't replicate the success as they don't have one strong character to wrap everything around, nor an end point for anyone to get invested in seeing.
They aren't the new kid on the block anymore. I think people were lenient on their writing deficiencies given they were the first to try a wider universe, but we are almost two decades out from this universe getting its start and every deficiency has arguably gotten worse since launch.