Not the sexism, but the rather grim view of human nature (which the work ultimately argues we just have to learn to live with).
Blame that on Da Ponte, not the production. Seriously, would you want to see such a downer of a production? Would you want to see a Nozze that emphasizes how much of a shit the Count is, and how wrong droit du seigneur was? That would override the beauty of the music, and make the production no fun at all.
Now, as then (maybe even more now? IDK, this is what I'm living through), people need a bit of escape from the real world. And this is a hell of a lot better than, say, Real Housewives. Not saying i don't go to shows that emphasize the crap going on today, but if this is the kind of circus I'm offered, I'm okay with that.