I was there 12/13 - 12/17 and it was crowded, but not holiday week crowded! I went once for Jersey Week/Veteran's Day in November pre-covid and that felt more crowded than this December week. World Showcase felt very crowded walking around a couple evenings, but other times wasn't bad. We got a lot done, even with waiting in more standby lines than I was used to with Fastpass (we did have
Genie+, but did not find it as effective). I would definitely go at that time again, especially because I loved all the holiday decorations and events.
We stayed at CBR and also thought the skyliner was great! Longest wait was getting to Epcot for rope drop and leaving Epcot after closing. We hopped around between Hollywood Studios, the resort, and Epcot a lot because the convenience of just jumping on the Skyliner was so easy.