Last year I got stuck on Day 12 for a full week, and thinking about how to solve it consumed my every waking moment. I think this year, I'm going to be kind to myself and not participate so I can really enjoy the winter break from work.
One reason I didn't enjoy it was that I felt the days don't build on each other well. So you get little code reuse. It was continually changing requirements, so it was especially like work.
In 2019 he built up about 12 challenges using a VM, for Intcode, you had to construct. It was poorly received because without a working version (developed over the first few Intcode challenges), you couldn't solve the rest of them. He hasn't done anything like that since, though I thought it was probably the more interesting series of challenges.
The problem with continuity across days is that the later days can be blocked by the earlier ones, as they were in 2019. That partly defeats the purpose (or structure) of the challenge, where you can mostly pick any day and try it without regard to earlier days or prior years.