I'm not Christian, neither is DH, and we have no family in this country - so actually for me it's a rather nice day/week doing the little traditions we've made up for ourselves.
Having said that...
The horrible cycle of spendspendspend+foodfoodfood, followed by debt + diet. Horrible to see every year in its grim inevitability.
Tat. Xmas jumper day (DD's goes to nursery with a hugely deprived intake - what the fuck were they thinking asking for 2 year olds to come in special jumpers?), gifts bought for the sake of it/with no thought to the recipient, the MN threads on the 25th/Boxing Day about gift-related drama.
The Next Boxing Day sale, and others. It's like we've been primed to consume and spend, short break on the 25th, spend some more. Obviously anyone who wants to partake, well, it's their money and their time, but I dislike it.
How the train network somehow conspires to leave a significant proportion of the country stuck outside Bicester for several hours every year.
The way it accentuates family drama.
Having said that, every year we walk up to the church at the top of our road, watch the crib service with friends, sing carols, and then walk back home admiring the trees and lights up along the road, before ordering a Chinese takeaway. And it's one of my favourite afternoons of the year.