It’s the week before Naxx, people are their most bored with current content and Shadowlands literally just got released along with it being the holidays. It’s perfectly reasonable for Classic to not have any high/full servers at this exact moment.
I wouldn’t be surprised if the servers for classic are slowly dying out, but are waiting for Naxx to hit, and majority of them are just raid logging. Which isn’t unheard of for wow at all. People play by the patch, or get bored, and start to play less to play other games.
Nice necro btw.