I don't dislike everything about Christmas but I think it goes on for too long and is over-hyped.
Both DH and I come from families who don't expect lots of relatives to get together for Christmas dinner so it's just us and our young adult DC at the moment - I would expect DC to spend it with their own spouses/partners when they have them. I'm also not in the least religious so it feels a bit wrong somehow to be making a huge fuss about "someone else's festival." DH was brought up vaguely religious but it doesn't really play any part in his life any more.
My ideal Christmas would consist of:
Putting up some decorations some time around the 20th
Sending cards only to people we cannot wish a happy Christmas any other way ie older relatives who don't use e-mail or social media
Work Christmas dinner and possibly a Christmas lunch with some friends we do an outdoor sport with (we didn't do this last year, but most years we get together, do what we do and then have a pub lunch afterwards - this is fun)
Evening visit to a Christmas craft market, with mulled wine etc, as late as possible in the month
Christmas Eve candlelit carol service (yes, I know, I'm not religious, but this service is rather charming) followed by not particularly Christmassy pub food
Exchange of presents with immediate family on Christmas morning and traditional roast lunch or dinner (which I cook). Long walk at some point during the day.
Decorations down by New Year's Eve
It wouldn't be an endless round of shopping, eating, drinking and having decorations up for weeks and weeks. DH is a bit more into it and we usually come to some acceptable compromise. But there's a small part of me that would really love to spend Christmas completely alone one year and not do anything at all except possibly have some roast chicken.
If anything, I'd slightly rather celebrate the winter solstice, when there is logically something to celebrate.