Really good point, Ding. Actually the concept of sacrifice itself couldn't be more pagan & superstitious....yet the apostles didn't have an issue.
I think there were servants of God who celebrated birthdays (Lott's children) but the Borg wiggle out of that one because the translation is 'loose'.
R&R yes a lot of acceptable celebrations are of recent, American origin - too new to have been banned in the olden days by Rutherford/Knorr/Franz etc
Beth yes Isolation from society with the bonus of more disposable ca$$h for Witchtower!