I see it as more of a function of Disney not keeping up with adding new attractions (and ride capacity) as the crowds grew. They purposefully chose to try and maximize every ride slot on every attraction (through FP+) instead of adding new things to keep up. Yes, I know they have started adding new things (finally). But they have a lot of lost ground to make up for. And in many cases they have closed things so are merely replacing things.
Indeed. And, IMO, the best solution is to put all future new rides in all the parks except MK. They all have capacity to spare, but they each have around 9 rides while MK has 27. They'll never be able to pull from MK until their number of family-friendly rides increase.