It is often said that the Church has never issued a dogmatic formulation on moral teaching. That most of her teaching is by the ordinary magisterium.
Two remarks. First, the second is true, the first is false. Most importantly, however, there are SCORES of infallible teachings on morals. E.g. masturbation is intrinsically evil, etc. Literally SCORES of infallible teachings on morals. The ordinary magisterium, teaching on a matter of faith and morals over a period of time, with moral unanimity, indeed teaches infallibly.
Second, Lyons I issued this declaration:
“Concerning fornication, which an unmarried man commits with an unmarried woman, there must not be any doubt at all that it is a mortal sin…” D 453.
This is a clear declaration of the Extraordinary Magisterium.