I'll be very surprised if there are any serve-yourself buffets when cruising first returns. Maybe after a year or two of not having any Covid outbreaks, they'll come back. But I think when most of us take our next cruise, a crew member will serve us at the traditionally buffet restaurants.
It's not just about serving yourself at the buffet. Everyone should wash their hands right before they eat anyway. It is really gross to go about your day touching things, your shoes, doors, etc, and then picking up food with your hands. That is how the majority of people get sick. I have worked in food for decades and a very small amount of people actually wash their hand before they eat. We always order our food, then go and wash our hands before we touch any food. That is why I hate bathrooms with the air dryers instead of paper towels. We use the paper towels to open the door. The amount of illnesses that can be reduced if everyone was just wash their hands before touching food would be dramatic.