This is really it in a nutshell. People will point to Pandora and Star Wars/Toy Story expansions and say "see, Disney IS doing something" - but the problem is they waited far too long to get the ball rolling. Epcot has fewer attractions now than when we started going 15 years ago. I believe the same is true for DHS. And while AK has added a headliner (one that I love btw) it still never had enough going on to keep people from rope drop thru dinner. At least people used to stay until the parade in late afternoon, but that carrot's long gone now. So what happens is everyone's all in on MK for the majority of their park days. We used to schedule 2 1/2 days of a weeklong trip for Epcot, now it's one day or one and a half days tops. We dearly love AK bit we're done before dinner and if we have park hoppers are looking for something more for the day. And we've never set aside more than a whole day for DHS and now we just skip it. this is why there's a 'capacity' problem. They fill the rooms on property and then on any given day most of those people are in MK instead of distributed among the four parks. Sure, when the new stuff is completed this will be alleviated but for the next few years while it's still under construction their reputation is going to take a significant hit from the 'OMG the crowds/waits/prices' reviews online.
TL/DR: Disney has done too little, too late, and too slowly.
