You fix the over crowding by giving the crowds more to see and do property wide. The new Cirque show is a good example.
Magic Kingdom’s announced Main Street theatre would have helped a lot. MK could also open up Diamond Horseshoe as a performance venue again, reopen closed restaurants, bring back quality entertainment that’s been cut in storybook circus, fantasyland, liberty square, tommorowland, Frontierland, and Adventureland (Main Street is literally the only land that has regular live entertainment.... with the one exception of Main Street philharmonic doing a set in storybook circus).
Running parades day and night. Right now they should be doing FOF as a night parade. Night parades help to distribute the crowds since many guests will choose fireworks OR the night parade and not both.
Running attractions at maximum capacity would also help.
The problem is not the crowds....