I understand your point, especially for Jewish Christians, from the point of view of cultural continuity, but it was decided at the Council of Jerusalem that gentiles would not be bound by the Torah in any way.
That being the case, mandating the observance of any of the Torah festivals would be wrong.
That said, I think it’s always a mistake to miss the opportunity for a good party. Again, Purim should be much more widely celebrated.
Hamantaschen for everybody!