Modern encyclicals aren't written in Latin anymore. They're drafted in Italian and the title is the Latin translation of the incipit.

Indeed, the beginning of the Italian text is: "La magnifica umanità creata da Dio si trova oggi..." from which, Magnifica Humanitas.

For those who don't know why that's interesting: The tradional practice for creating these kinds of texts is to first write an editio typica in Latin. This Latin text is then the basis for translations into vernacular languages.

Yeah, I don't know how they expect the people of Latin America to read this.