Of course, you know all too well that there were never any written documents by pagans about paganism. All of the written information only comes from the colonizing Christian religions
The main point was noting how modern the tradition was. It was something that only caught on in the 18th and 19th c.
Enough people wrote about Christmas to know it wasn’t a Germanic tradition prior to this, which is ultimately what the claim relies on.
It's not like there are an absence of alternative reasons someone might have a tree. Whether they were recreating the “tree of paradise” from seasonal mystery plays, mirroring local myths about trees miraculously blooming in deepest winter, or just making a pretty decoration for the kids we will never really know the exact reason it caught on (my guess is it’s mostly the latter).
As well as the large time gap, that it seemed to be something more common in Protestant households also makes it seem unlikely to have been a pagan tradition kept alive in a different form.
Before Christianity the people were indigenous with the land
This is a bit of a romanticisation imo.
They lived in towns and villages same as they did after they became Christians.
As much as any pre-modern group, Pagans exploited the land and destroyed forests for agricultural and commercial reasons when it suited them.
They also weren’t even indigenous in most places, they migrated and colonised.
The big mistake on interpreting pre-Christian religions is to see them through the mind set and metaphysics of the transcendental Christian and contemporary western view of the world. There was a spiritual connection with the land dominated by the forests. The sacred nature of trees continued long throughout the Anglo-Saxon world in England. We do know that although they did not write down anything their relationships with the land the oral stories did not stop there. They continued in the folklore, the fairytales, and rituals. How long these relationships lasted is well represented in similar cultures of Ireland and Iceland. I agree that the person dedicating the tree to celebrate Christmas was doing so for celebrating Christianity and not paganism. But the importance and connection of trees and the land is more of an indigenous metaphysics which did not die out in the conversion to Christianity. The importance of trees and grooves was well known demonstrated by the stories of St. Martin destroying sacred groves.
I certainly agree that we shouldn’t assume pagans thought anything like modern folk, but medieval Christians also thought very differently.
As a result, people often assume anything that doesn’t make sense to our modern mind must be a pagan relic as if these societies were incapable of innovation as opposed to appropriation.
Liking trees isn’t inherently pagan though, neither is finding forests mystical or spooky. I'm sure you know that from when you were a kid.
Modern humans like trees too, and this isn’t simply because their ancestors were pagans who taught themselves to like trees. Humans intuitively have an affinity with nature and turn this into aesthetics, stories and traditions of all kinds.
I agree cultures and mythologies don’t instantly die out. But that doesn't mean they are the driving factor in all behaviours carried out in perpetuity.
At some point, the ancient Egyptian or the medieval German mythos stops being the most likely reason a contemporary person likes trees.
No doubt some modern interior decorator will find something novel to do with a tree or shrub every now and again, but this isn’t being driven by the sacred connection between pagans and the land. It’s just an aesthetic.
It’s easy to construct a narrative that suggests it’s really a subconscious attempt to recreate a sacred grove and it’s completely unfalsifiable. Ultimately, it’s mostly just us projecting our preferences onto other people. Projecting paganism on to a 21st C person, is little different from doing the same thing to a 19th C person.