I’ve always thought these other holidays like HumanLight and Festivus were kind of lame attempts to compete with Christmas. After all, Christmas has a lot of cultural evolution behind it that has caused it to succeed very well.
Everyone should know that Christians have appropriated many older customs to form this holiday to try and make it their own. I don’t see why we can’t appropriate it for ourselves just as they did. It is already well on the way to becoming a “secular” holiday anyway, so maybe we can just push it the rest of the way.
There are many Christians who don’t understand the history of why it is sometimes abbreviated as “Xmas,” and they object to that abbreviation because they think it is “Xing out Christ from Christmas.”
Rather than trying to continually enlighten them about this issue, why not embrace their misunderstanding? We can say, “Yes! that’s exactly what we are trying to do!!! We are going to celebrate Xmas just like you celebrate Christmas, but without the Jesus BS.” We can still have the tree, the lights, and the gifts etc., but without a Jesus in the manger.
If Christians can steal it from pagan traditions, then we can steal it from them.
It could also be considered somewhat edgy, just like the X-Games relate to the Olympics. We could add our own extra flourishes to replace those that we are excluding (possibly crowning the tree with a Flying Spaghetti Monster rather than a star, for example).
I think it may be easier to appropriate it than to compete against it.