"We declare, say, define and pronounce, that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff."and then goes on to analyze the various possible responses to this kind of a Papal statement, and how it might still make sense, with all the development of doctrine that has taken place since 1302.
Long, but worthwhile.
The commonest response is ... "oh that's so darn outdated/medieval/pre-Vatican II" (and, of course, we all know that the Church really started only in 1965, right?) (this is "position 2" in Mark Shea's scheme)