I like them, and I think it’s a bit sad that it’s dying out as a tradition. I have whittled my list down a lot these days, but for the few left I still enjoy choosing nice ones that I think the recipient will like. I do add an individual message, not just names! I agree that younger people are stopping sending them, but I still have a fair few people on my list who are older, often single or bereaved, eg. former colleagues or friends of my parents who were kind to me as a child, who I know still enjoy and appreciate a card at Christmas.
We all know that Dave at work or one’s thirtysomething friends can text or Slack or email instead. But for Auntie June who lives alone half the country away, or Reg the elderly widower of your godparent, or your mum’s best friend who used to buy you lovely books when you were a kid, or your mentor from early in your career who’s now retired and who you want to show you still think of — those are the people who really do appreciate a card, and honestly I love sending them, and choosing something nice from a museum or something with cats on for Auntie June who loves cats, or whatever. And I still have a few friends my own age who like sending and receiving them, too.
If you don’t care about them, fine. But I do think that being sneery about something someone else has done at their own expense, just to show they’re thinking of you even if momentarily, is way more déclassé than any “working class” card (nice stirring there, OP 😆)