A tiny loud minority isn't why this film is bombing. Barbie, a female led movie based off an old toy line, did $1.4 billion dollars and that movie was absolutely trashed by the far right. Marvel's track record since Endgame has been very inconsistent and judging box office returns for the past few years, the super hero genre itself isn't as popular as it use to be. Audience score on rotten tomatoes seems to be pretty good, so clearly the majority of people that ARE seeing it like it. There just isn't enough of them, which clearly shows declining interest in the genre.
I don't know if it's necessarily declining interest in the genre, but declining interest in the brand? Sure, I can buy that. The MCU is in the same position that Lord of the Rings and Harry Potter were: The shit everyone cared about is over. After you've cast the One Ring into Mount Doom and had your 10-minute slow-mo Hobbit pillow fight, it's hard to say, "Wait, there's more," and get people excited about it. Especially if "more" means watching Eddie Redmayne chase griffins and once in a while someone says "Dumbledore."
Marvel spent 10 years building up to Thanos, and then the Avengers beat him. Iron Man is dead. Captain America is old. Black Widow is dead. Thor is in space. The Hulk is ... somewhere else. Nobody ever cared about Hawkeye. The Guardians of the Galaxy broke up. Spider-Man went off the grid. For a general audience that doesn't geek out about Moon Knight or Ant-Man, it sure looked like the story was over.
Maybe by pivoting to the X-Men they can get some of that 2012 mojo back, but we've already seen the X-Men ... twice. For that matter, we've already seen the Fantastic Four twice. Marvel needs to give people a chance to miss them.
And I feel this also ties into just how bad the advertising was. They had a decent first trailer with the whole "Intergalactic" thing, but with the strikes going on, all they had to rely on were commercials that were on the level of that ... Disney space movie that came out a year ago. Not Lightyear, but the other one. The one where the guy hates his dad or something.
So their big advertising push was, "Go see Marvels. It's a Marvel movie. You like those, right? What's it about? Who cares? It's Marvel!"
Once it was apparent that wasn't working, they tried to make a big deal with the last-minute final trailer, which was, "Remember Iron Man and Captain America? Remember Thanos and Endgame? Well, maybe this movie has something to do with those things. Who's to say? Marvel, am I right?"
There was just no identity to the movie outside of that first trailer. It was just Marvel content being sold as Marvel content.
I'm half-expecting them to start showing the mid-credits scene in the commercials, like when The Incredible Hulk wasn't doing great in the box office and they straight-up told us that Tony Stark shows up. Which was still less sad than the Ang Lee Hulk movie, which had commercials based upon how bad the reviews and word of mouth were and how you should just go check out the movie yourself to see how you personally feel about it.