I’m not sure where the pushback is coming from on @MrDibble’s part that “Christmas isn’t Christ’s Birth any more for most people” means that its origins are therefore irrelevant to modern Jews, in particular.
It’s not like, say, in Japan, where Christmas has become a HUGE deal despite very few of their population being Christian - it’s become a winter holiday to decorate, to exchange gifts, and to have dinner together, usually with a romantic bent, more like a Valentine’s Day in overtone than anything religious. An angel (Annuciator) on top of the tree, versus a star (of Bethlehem), means as little to them religiously as putting a Smurf or a baseball up there would be.
But that is how Christmas was introduced to Japanese culture: secularly, and the way it is done now was largely constructed after WW2. In fact, one aspect of the “Japanese Christmas Dinner” is that it be comprised of Western food, especially fried chicken, and especially (thanks to successful advertising) KFC. I am not joking. People book reservations at KFC for Christmas weeks in advance in Japan, to have a Christmas date with their girl/boy friend.
Now think about the history of Jews in Europe over the past 2000 years. Many pogroms erupted around Eastertime, for obvious reasons (often intentionally inflammatory sermons about how “the Jews killed Jesus” and Passion Plays depicting them demanding his death of Pontius Pilate, abusing Jesus on the way to Calvary, etc.), but there is a list of Christmas pogroms as well. Basically, it was a time where being not-Christian was not just a “eh, so don’t go to Church then” thing, but an active reason to hunker and bunker down in mortal fear for your life and possessions.
And not all pogroms took the form of mobs chanting “kill the Jews, take their stuff, and burn their homes/stores”. Some were mobs doing forced conversions. Which is another terrible form of violence.
So, yeah. Two thousand years of that kind of fear - even if “not every year” for 2000 years - that doesn’t just go away because it’s 2021 in America! Ha ha! Nobody does that any more! … For now!
I mean it has for some, I can’t say it hasn’t, but I fully understand the Jewish take that “Christmas is fundamentally non-Jewish” in way that goes way, way beyond “because it expresses celebration of Christ as Savior”.
I do know of “secular Jews” who put up Christmas trees and wreaths and tinsel door/house decorations, burned a Yule log, who treated it as a Winter Solstice holiday while specifically dodging the relgious corners (specific carols like “Silent Night”, no angel iconography or Nativity setup, etc.).
But far more common is the pointed non-observation of Christmas. At least in conventional ways. Have you never heard of “Jewish Christmas”? It means “we go out to get Chinese food and then see a movie”. Because Chinese restaurants in the US didn’t close on Christmas, and movie theaters have always operated on Christmas Day evening - it’s even a common opening night for some blockbuster movies.