It's also canned a tannenbaum. The terms are interchangeable--I suspect it only ever got started getting called a "Christmas tree" as a result of Christian 'assimilation' efforts of pagan holidays, which was common in the early days of Christianity. After all, Yule used to be celebrated following the lunar calendar, so it was about late December to early January. But it was in fact the process of Christianization that moved it to December 25th in order to correspond with what now is called Christmas. Of course, doing that makes it a lot easier to get people to acknowledge your holiday, but makes it a lot harder to get people to celebrate it the way you want them to.
I'm aware of that--I used the word along with the general meaning "not Christian, Jewish, or Islamic (in a religious context)".
You're confusing paganism (which is a lot broader than the narrow definition you provided) with Wicca, I think.
The 1500s isn't THAT modern. And whatever you're talking about above isn't what the tree started as; the first trees were actual fir trees, not just a few branches (indeed, that's what "tannenbaum" is German for, and the tradition of the tree is Germanic in origin).
Not sure what the point of your post was, but I'll reiterate that anyone can enjoy this time of year for any number of reasons--"Christmas" as we know it is not something even close to exclusively Christian, and even atheists may call it that instead of "Yule" or whatever else for no other reason than force of habit. Once more, whatever.