What I noticed about the article is the guy who said that, realistically, after Endgame, the MCU will probably undergo a relative slump which is almost inevitable after the big event that they've been leading up to since the beginning. Mind you, relative slump meaning still making buckets of money but not quite as much. He may be wrong, of course. But if it does happen, we'll be right back to people insisting the genre won't last.
Also, they are very limited in what they can set in the past. Anything in the past would have to be secret heroes that the general public never knew existed as anything else would contradict established MCU history. They could reset history with Endgame but I don't think that's a good idea. This isn't a comic book. It's movies for general audiences. "This movie that you saw and have the DVD of now never happened or happened differently than what is on your DVD" is not going to go over well.