Imagining that you can't use a date also used by pagans because they were, in fact, pagans is a violation of the principle Peter set in his discussion of what foods were acceptable, which were prohibited, and what about food sacrificed to idols.
I don't think Peter showed any concern at all for which day the food was sacrificed, and neither should we!
Last thing we want as Christians is for the pagans or their successors to get the idea they can whipsaw us around and make us do things. We do what we want, when we want, for our own reasons.
Really, it DOES matter. Does YHWH change? Did YHWH ordain His Holy Days? And what is the purpose of those days?
It matters because those TRUE Holy Days, and their purpose, go wanting. I doubt that more than 1 in 100 Christians even know what they are.
Last thing we want as Christians is for the pagans or their successors to get the idea they can whipsaw us around and make us do things.
LOL! They already have.