I think you’re confusing a number of different things here. Lady Macbeth of Mitensk (and the source story) involves a rape, just as it involves scenes of wrestling and a whipping. Some productions present this graphically, others not. Of the ones that do, I imagine some are doing it to critique the patriarchal society in which the opera is set, while others appear to think (like much of tv and film) that rape is ‘entertainment’, something also find deeply disturbing. Your teacher was right to warn you, obviously. The ROH had a production of Rigoletto that involved a rape (not in the opera) to illustrate the cruelty and misogyny of the Duke’s court, which I found disturbing, but not inappropriate in this opera — I sat in on rehearsals, and was satisfied the actress in question (it wasn’t a singing role) was properly treated by the director and crew.
It’s a fact that opera now requires different things of its singer — they’re now required to act well as well as to sing well, and to dance, and often to sing (over a full orchestra and ( in difficult situations — eg upside down, lying down, running through the stalls, on a trapeze et.
I don’t know the podcast (could you say what it was?), but it can be a brutal world to start off in as a young singer, regardless of sex. I know countless singers who’ve dropped out because the casual gigs, insecurity and continual travels are wearying. Some bastions of the classical music world, like the Vienna Phil, were massively patriarchal , all-male institutions until v recently. Marin Alsop is very interesting on being a female conductor. And traditional opera centres on female vocal beauty, but very often ends with the death of the soprano! It’s a weirdly lopsided world in which female roles are key, female stars very powerful, but their characters are rarely alive by the time the curtain falls.
There are loads of operas by women, but part of the problem is a repertoire calcified around a few male-authored classics, so even when they’re performed, it’s seldom. Look up Ethel Smyth’s The Wreckers, or anything by the 19thc singer Pauline Viardot, who also composed, or Judith Weir, or Kaaija Saariaho.