For me, personally, my two biggest complaints right now are the cast member and entertainment cut-backs. And by entertainment I mean the smaller shows or performances, not the nightly spectaculars or any parades.
So, in other words, the people who make the magic in the park. If WDW could find a way to automate the entire park, I'd never go again. The cast members add that special touch. They add the pixie dust. They make the magic moments, fix the problems, make people smile.
(Oh, and Disney, if you're listening---they're the ones that take awesome photos. Ban the darn boxes!)
The entertainment is part of what people can point to and say "This is part of what I'm getting for my ticket." when Disney's busy adding layer upon layer of up-charges. The entertainment helps disperse crowds. The entertainment can be a pleasantly unexpected part of a day at Disney, if things pop up that are not mentioned in the time guide. The smaller entertainment acts & shows are things you can look forward to at different times of day, with no line, no Fastpass, no ADR, no dessert party seating. And people often need that. They need to know there's a fun thing they can do without sitting on the sidewalk for an hour saving a seat or planning 3 months in advance. Plus there's a playfulness to so many of them, and that again comes back to the people performing.
Keep your people, Disney. You need them. They are the ones who breath life into your parks.