This issue, among others, is the reason the Council of Florence is tricky, and not very suitable for people trying to discover the Church’s teachings on issues, at least without reading a great number of books on the context of the Council.
The part that you quote is from the Bull of Union with the Copts. This and the bull for Union with the Armenians have not been considered by the magisterium or by theologians as an authentic expression of the magisterial teaching of the Church. This is why it is not in the Catechism and why priests don’t say anything about it.
The decree for the Armenians, for instance, follows almost to the letter the sacramental theology of St. Thomas Aquinas, and says that the ‘matter’ for the sacrament of ordination is the handing over of the instruments. Pius XII seemed to have no problem with the fact that the Council of Florence said this, when he said that the matter for ordination is the laying on of hands (I’m leaving aside the question of whether, for certain sacraments, the Church can ‘change’ what the essential rite is).
Simply put, accepting these statements creates a whole host of contradictions with other teachings. The Church doesn’t teach one way or the other on the issue of male circumcision, except for the valid principle which Florence correctly states, that a Christian cannot do it thinking that they are submitting to a requirement for salvation.
Even if this document were authoritative, what it is really speaking about is the ritual practice of male circumcision as practiced in Judaism as part of the law, imbued with religious meaning, not the medical practice of it. This is an important distinction.