I like the idea of seeing all my siblings at one time (except for that one cross country one) and seeing my nieces.
But I hate all of Christmas. Everything about it, from people having decisions up the day after Thanksgiving, to them staying up until February, the fact that most songs from this time of year talk about Jesus...
The way it (this is a little redundant) takes up the whole month is the 2nd biggest part. No other holiday gets more than 48 hours of observance, including prep time. Even extra Halloween candy is done being talked about after a day or two once the discounted stuff is bought up.
The biggest part is the religious part. My siblings all know how I feel (most of them share the feeling), but my parents didn't and I aim to keep it that way unless point blank asked about it. That conversation will not end well. I've already told them that outside weddings and funerals (and hopefully not even then) that I will not ever step for inside a church again. My family was not exactly cult level, but it bordered on it. When I finally came out of that bubble it was rough. Really rough. I didn't wanna claim religious PTSD, as I don't think it's that severe, but churches bother the hell out of me (pun not intended, but it works).
Growing up Mom had way too many decorations (in general, but especially Christmas ones) and just bringing them all in the house, and being made to help out them up was a PITA. I think part of me figured it (religious faith) out early, but it took until I was almost 31 to figure it out. But even then I was annoyed by how much work it caused.
So (TLDR) I wish it was just a day or few days where you'd hang with family you might not get to see any other time of year.
Literally every other part of it can just be forgotten with no ill effects.