It's not a definitive teaching concerning faith and morals, so the answer is "of course not".
The Gregorian calendar is not perfect, just a lot closer to astronomical truth than the Julian calendar was. A further calendar reform may make sense at some point.
From what the OP was saying it sounds like this was very much about matters of faith. Wasn’t there much concern about the “proper” observance of Easter as well as the various feast days and wasn’t this the whole reason why Pope Gregory did it in the first place?