I asked Chat GPT and these two points seemed to be the most salient:
“Secrecy and Oaths: Freemasonry involves the taking of oaths and vows that are often secret and binding. The Catholic Church opposes such secret oaths, especially if they conflict with one’s obligations to the Church or are perceived as a form of allegiance that supersedes loyalty to the Church.”
and also
“Historical Conflicts: In the past, Freemasonry has been associated with anti-clerical and anti-religious movements. Some branches or historical instances of Freemasonry have been seen as hostile toward the Church and its teachings. This historical conflict has contributed to the Church’s distrust and prohibition.”
“In 1738, Pope Clement XII issued a papal bull called “In Eminenti Apostolatus Specula” which was the first explicit papal condemnation of Freemasonry, forbidding Catholics from joining Masonic lodges due to the perceived conflicts with Catholic teachings and the potential for influence on members that could be contrary to the Church’s beliefs.”
“Subsequent popes have upheld and reaffirmed this prohibition, with the Congregation for the Doctrine of the Faith issuing a statement in 1983 reiterating the incompatibility of Catholicism and Freemasonry.”
I can’t vouch for the accuracy, but it does seem like there’s some good avenues to explore if you wanted to verify the statements independently.