No you're the moralist. You want to control what people do. Even before death.
Whether you stop existing or go somewhere else, that's irrelevant. What's relevant is ONE person = YOU telling others what they should do. That's moralising. If it works for you great, but don't dictate to others.
That's your moral view. What burden on what society? Let society speak for itself. Don't speak for the society and decide what is and what's not a burden. At most you can say: "My body is a burden. Flush it or vaporise it. Etc." That's fine. But that ends with you.
So you're saying people don't contribute when they're alive? And who decides what a contribution is? YOU. Surely you're contributing by laying this wonderful dogma on us.
Again, who decides this? You? Stop moralising.
Also I don't see how organ donation will solve the problem of full cemeteries in SA.