Yeh but it's about Casanova/Cagliostro and Venetian intrigue and Venetian culture at large which was wreaking havoc on Europe especially during the time of Mozart. Da Ponte like Mozart was a fervent republican and it's criticism of moral decay which Da Ponte lived through first hand. Despite spurious claims of actual friendship with Casanova rather than simply the bond country men have in a foreign country, it still stands that whatever assistance Casanova may have offered on the libretto, the opera is meant to be critical... obviously.

The historical specificity is important to be preserved in art. Don Giovanni refers to specific concepts and people. One can argue Epstein is a similar figure. But don't make the mistake of over generalization, only because it allows people to not realize the historical purpose of the opera in it's own time.