Same here OP, just DD (19) and I, ex died 15 years ago and we rarely see ex's family.
Use to do the big family gatherings with my family but as all 'kids' are now adults, my dad's dead, mum's in a rest home and other family issues joint christmases seems to have fizzled out.
Last year it was just us two, I wouldn't say it was depressing but pretty boring, like any other day but with a fancy meal and lots of chocolate.
Although we have definitely made some changes, made pancakes and the we had a joint Christmas with my recently divorced friend and her daughters which was very lovely. Followed by a long walk on the beach together, then a good film.
We are not focusing on the day itself, we are visiting other friends during Christmas limbo and going to spend time with my brothers and their families in the New Year.
But omg I am so glad I do not have to suffer Christmases with my ex in laws anymore, there are bonuses!