The Universal Tradition is separable from particulars even if it must ultimately be, as often as our nature requires it to be, expressed in particulars. That is exactly how traditions can be lasting or perennial.
I don’t doubt that Christians have from the first honoured the nativity (or birth) of our Saviour: I can see how my family’s very English quasi-Germanic Christian tradition, predominant and widespread in North America, for example, is an expression of that Tradition; however, it would be a grievous mistake to think that the first Christians i) sang the carols we do on ii) December 25th, iii) set-up Christmas trees and decorations and iv) went shopping to exchange gifts. Not one of those particulars should be confused with the Tradition itself but are rather an expression of it. Indeed, as the name suggests, its earliest and most definite expression or emphasis probably had a deep connection with the Mass or the Eucharist at first. Even that connection proved highly dissociable though obviously natural and logical and I’m sure in many places actually obligatory (i.e. you have to attend Mass for/on Christmas or Christmas Day). But even that obligation, possibly, was itself a development from a more primitive tradition. Moreover it is in fact the Church that promotes the celebration of Christmas: it is not a divine ordinance as far as I know though, to be sure, it is an event recorded for our knowledge and memory in the Gospels. We are obliged by God, however, to obey and listen to the Church.
I can sympathize however with someone who associates any one or all of those particular expressions of Christmas I mentioned above as being “the Tradition” (as being basic or part and parcel to Christianity, say); however, I know -largely from history - that it is simply not.