I mean, it kind of follows Marvel’s own historic struggle with continuing stories past their natural conclusion.

The cinematic MCU had parallel stories of all these different hero plot lines that would intersect in interesting ways. That takes a lot of planning and building, all leading to a single nexus point where it all came together.

And it felt impactful. All the build up led to an epic intergalactic showdown. Twice.

Then afterwards, what are you left with? From an MCU standpoint, everyone goes back to their small little slice of the world/galaxy to do their thing, with some cameos of other heroes they befriended along the way.

To try to bring some level of stakes back, they spiraled down the multiverse paradigm. Just like the comics kind of struggled to make things interesting after the heroes finished their primary arc.

Add on top of that the real world issues of actor burnout on characters they’ve played for over a decade, and you’re going to have trouble keeping up with expectations.

There are still things to do. But they’ve burned through the primary material like origin stories and top villian arcs, and the original actors have probably fulfilled their contracts and are probably not that interested in renewing.