Do I or you have any reason to say that the Jehovas witnesses in this case are not just being clear about what's a more fundamental point in christianity?
I once asked here about if people got ascencion day off work. One person expressed he'd not heard of it before, and suspected it to be a fringe thing of smaller christian sects (like JW), but the ascencion is a central thing, and the date marked by every single denomination
I didn't think it was clear as a Christian and the Catholic Church clearly doesn't either. There is a theme of a spiritual reality distinct from the material world, which I suspect has origins in syncretic, classical metaphysics. I was never that curious about it personally, because I didn't a have a strong belief in the dead being able to observe life, which would make the time of the afterlife less significant. And if it's eternal, what difference does a few years, centuries, millenia, geological or astronomic ages make?
As for Ascension Day, I see that it is formally exalted, I don't see why it would be worth celebrating more than Easter, Good Friday, Pentecost, Christmas or whatever the holiday about Gabriel visiting Mary is called. Maybe if one focuses whatever Jesus started doing after ascending to Heaven, it's more significant, but I think he ascended because he had already accomplished the work of his incarnation. Although maybe this does demonstrate a difference between formal Christianity and popular Christianity. One of my teachers told us that Easter was the most important holiday in the Church's calendar. I don't know what to make of that information. Be slightly more Christian on that day? Similarly, the attributed importance of Ascension Day is easily forgetable without celebratory traditions.