I've just watched the parks panel from D23, and one thing that stuck out was Disney Genie. It's purpose is to "optimise" your day at the parks.
And there lies the massive issue that only seems to exist at Disney World, the near to the minute planning that Fastpass+ requires. Holiday should be about fun and enjoyment, not an optimisation problem.
Disney are happy to just keep cramming people in it seems. Ultimately their goal seems to be "making the park cope better with more people" rather than "stop everywhere being packed year round". Even designing all their rides for maximum capacity, it's not going to stop insane crowds around the parks and for night shows.
Maybe Universal will poach some customers with Epic Universe but I think Disney are going to have to stop trying to squeeze so much out of what they've got and build new parks (whether at Florida or somewhere new in the US)