This year I paid more attention to how clean-up from the family holiday meal occurred. We had disposable plates but real silverware, and the food was set up buffet-style. Everyone either brought their dirty plates/silverware back into the kitchen on their own, or another guest voluntarily took their plate when they saw the person was done eating but was still at the table chatting. The two hosts (people who live at the house) put silverware in the dishwasher and the plates in the trash. When it came to divvying up leftovers, anyone could fix a plate for themselves or someone else (like my grandma). If a dish needed special preparation--like bar cookies that hadn't yet been cut up--usually the person who brought the dish did that, then people took what they wanted. Anything that was left, the hosts packed up however was convenient for them.
One open question is what happens to the extra leftovers--my parents and I bring desserts, which WILL NOT come back home with us per mom's instructions, so we abandon them at the hosts' house. Other guests are free to take some, of course, but they are not coming back with us. If we want the container back, we transfer them to disposable plates or some other receptacle. But, a cousin brought creamed corn in a crock pot--kind of hard to plate and carry away, and I'm sure she wanted the crock pot back. I think they just carried the remains away still in the crock pot after everyone had gotten a chance to take some (i.e., did not leave the extra food with the host).
I guess it sounds kind of chaotic, but it seems to work for us. The only one in charge is the host, but they aren't telling anyone what to do, unless someone asks a question like, "What knife should I use to cut this?" Everyone just kind of takes care of their own piece--put your own dish by the sink, deal with your own leftovers--and maybe a little more (put someone ELSE'S plate by the sink as well), and the host deals with anything left. Disposable plates and cups (actually cans and bottles) cut down on a lot of clean-up, and the silverware was dishwasher-safe. If anything, there's sometimes too MANY people doing things, and Grandma gets two plates of food fixed for her, or the seven-year-old walks away with two plates of cookies, but that's nothing to get upset about (unless maybe you are the seven-year-old's parent!).
For the OP, I stand by my earlier advice, though I do think family dynamics come into play. In some families TootsNYC's advice would be perfect. Personally, I would feel uncomfortable 1) pushing other people to help and/or 2) refusing to help when asked; so if one more straight conversation with the host didn't result in changes, I would regretfully absent myself from the next gathering. Then I think there would be rounds of conversation--attend the gathering to see if attitudes changed--don't attend the next one if they haven't changed--conversation etc. until I saw that progress was being made, or I just stopped going altogether. If someone suggests it's petty to miss seeing your family at the holidays because you don't want to clean up? I would say, it's more
petty, and rude, to treat one family member as a servant at the holidays, when they have specifically asked for changes, and then complain when they don't show up to be ill-treated some more.