I take my tray up to the pool deck and put it on the bus station outside Cabanas. And room service isnt that great so we'd rather take a couple flights of stairs and get something from the quick serve.
Their wings are really good though so we always get those from room service
I dislike old food in the hallways as much as the next person (and I'm a bit flighty on vacation so have tripped over plenty of "hall dishes"), but I think that's a bit much. If that's what you want to do, fine, but I wouldn't label others as rude because they don't bus their room service plates to the buffet. Not to mention that means somebody from the buffet area has to come fetch the covers for the plates. I can't recall with Disney but many lines use different plates for the buffet and room service making it even more confusing for them.
Room service is offered (I hate buffets so if the dining room isn't open I opt for room service) I'm not going to forgo that amenity because I don't like their cleanup policy. I always call and regardless of cruise line or hotel am 99.9% of the time told to leave it in the hall, so that's what I do.
Some people are just rude no doubt about it (part of the reason I hate buffets is the amount of finger licking before touching the serving utensils or just full on sticking a hand in the trays I have seen). I also think it can be confusing. The few times I've been to the buffet, I've seen staff bussing plates but no station of bins to bus yourself. I tend to leave plates on the table rather than carry stacks around a crowded space wandering in hopes of finding where to go. I'm sure some on this thread think I'm rude.
Places where you bus your own food tend to have signage and clear stations with bins for trays, plates, silverware, etc. I'm always a little muddy on ships as I never see bussing stations.
I gather up my towels at the pool because there a huge bins for wet towels in various places on the pool deck so it's pretty obvious. If I saw staff picking them up but no place to put them or saw staff pushing bins for towels and gathering them up, I might leave them.
While I don't subscribe to leaving crud everywhere because people are paid to clean it up, I also don't subscribe to the whole notion that you're rude if you don't completely pick up after yourself everywhere you go.
I'm not going to leave piles of food that's dropped on the floor, but I'm not going to dig under the table for bits of crumbs when the cleanup staff have a vacuum.