Yes, I am.
You're attempting to reduce Christmas to nothing other than preexisting non-Christian celebrations with the serial numbers filed off. I already agreed it's partly that, but it's other stuff besides, and it's also other stuff that is intrinsically Christian.
There are several tacks one can take on the appropriation idea. One is appropriation, but another is accommodation, and a third is incorporation. None tells the whole story. It's worth noting that Yule itself is a synthesis of Germanic, Nordic, and Anglo-Saxon traditions whose origins fade from our view into prehistory.
And, if you can't agree that Christmas means something to Christians that it doesn't mean to non-Christians, well...

... I don't know what to say.