My wife and I saw the movie last Sunday. We walked in as the 3D showing in the same theater was wrapping up and I would say there was at most a dozen people in there. Our non-3D showing had probably 50 people in it. I would say that the room had capacity for 250 to 300.
I was very surprised at how empty it was.
We went to watch IW a week after it came out, Saturday, and the theater was pretty full, 90%.
We also saw Thor:Ragnarok about a week after it came out and theater was 70-80% full. We saw Black Panther almost a month after it first came out, and the theater was 60-70% full.
I got a feeling Marvel / Disney may be reaching the end of the money train after IW:Endgame comes out.
People need a respite from all the comic book hero movies, and something original and fresh. Maybe Avatar is just what the public needs in 2020 and beyond.
I agree with your last part a good bit and I say that as a comic book, Super Hero animation and movie fan, but they are close to a fatigue point. With all the stuff on Cable TV and Subscriber Series its ....a lot.