I actually did not find Santorini crowded when I went the November before covid. But I also did things a little differently. We got off the ship first thing in the morning and took the lift out of port. Then walked to the local bus to go to Akrotiri. Before catching the bus we noticed a fish spa near the bus station that would open later in the day. I always wanted to try it but they are not legal where I live. So we went to Akrotiri then the fish spa and since we still had plenty of time we then took the bus to Oia explored a bit and then took the bus back. The only thing I would not recommend doing that we did was walking back down to the ship. I am a huge walker. I spend about 2 hours a day just walking my dogs. But I would would not take that walk down again. It was very steep, slippery and covered in feces.