re: comic book movies -- fatigue, etc.
Even though I don't often share mainstream tastes, I think the movie-going public is pretty aware of the overarching meta of these various franchises. The halcyon days of the MCU are mostly due to the belief that it was all leading to something as a cohesive whole and that that endpoint was going to have a payoff, so all of those movies had inflated performance compared to what a disconnected movie starring the same characters would have had. Likewise, today, people know that there isn't a coherent larger story driving things and are opting out of most of the movies, catching up on whatever interests them on streaming as time allows. If Disney can recapture that sense of direction (or alternatively have each movie contain a can't-miss event -- 3 Spider-Men in 1 movie! Deadpool *and* Wolverine together at last!) then they'll regain plenty of the zeitgeist/event viewers.
For DC, you can't really point at the last handful of movies as representing any real trend. Regardless of the quality of any of the individual movies, everyone knew that they were the last, sad spasms of a connected universe that had had the rug pulled out from under it. There is no world in which movies like that will do well in today's market because (see above) there's largely a misguided sense that superhero movies need to "matter" to a larger story in order to get a large audience. Similarly, people know that the new Superman movie is the start of something new, though it remains to be seen what exactly that something will be. Gunn and Safran's plans seem to be ever-shifting other than knowing what the first 2 movies will be.
I'd categorize expectations for these movies like this:
$400m-$600m -- generic DC/Marvel entries
$600m-$800m -- name-brand DC/Marvel entries (Batman, Superman, etc.)
$800m+ -- zeitgeist releases (either through events(!) or overarching story)
The MCU's last two movies have been just at the bottom of acceptable, and Thunderbolts* is starting to drop off a little faster than Cap 4 did, so it's more than understandable that Disney would pull back a little until they can either focus things toward the next big story or find a way to bring budgets down just a touch for these lower expectation movies. These returns wouldn't be questioned so much if Cap 4/Bolts cost $120m each, like Venom 3 or Kraven.