Science Fiction

Agreed for the most part. The multiverse angle is to let them discard continuity as necessary, without doing so officially. They can recast the same roles when talent cycles out (or theoretically if it cycles back in, should ScarJo or Chris Evans suddenly decide they want a new deal) but also blend with existing cast when they want. They can tell stories that can be self-contained, but also don't have to be, and if a story is poorly received or a villain is just too charismatic, you get all the do-overs you need. It's like the all you can eat buffet of storytelling, but what do you when you can have anything but none of it seems appetizing? Audiences will intuitively understand that there's no weight to any of it even when seemingly important things happen, and that the narrative will be subject to the commerce, but not even in the still-slightly-risky predictive way it had to be in the past. You can't even write yourself into a corner anymore. The spectacle and momentary melodrama is all that's left. It's like going from prestige TV to pro wrestling.

As long as the quips are there, the smiles are big, and the action scenes being cranked out by the on-staff Action Scene directors, then the movies will still pull in a bunch of money, but it's going to be a little less as people care less about the overarching story; most of the DC movies had decent global box office numbers, after all.

Gone are the days where Marvel was putting an interesting spin on popcorn cinema, though it's important not to overstate it. The unprecedented level of interconnectedness led to interesting stakes and repercussions, and was a callback to the comics themselves and old-timey serials. The MCU movies were also fun with how they'd dress up superhero narratives in the clothes of other genres, though admittedly without really changing much: The Winter Soldier is not much of a spy thriller, but it is a pretty cool super hero movie pretending to be a spy thriller. Not going to lie, I'm still hanging with it, but it takes me longer and longer to catch each installment, and I walk away from more of them kind of not caring all that much about what happens next, just willing to find out when I can get around to it. Most of it is still better than DC stuff, but that's damning with faint praise. It's also less of an emotional beatdown than the grimdark backlash shows like Invincible and The Boys.

TL;DR: Marvel has a pretty high floor as long as the house style remains light and the production values don't slip any farther, but there's just not much special about it anymore.