This is perfectly put, there's a huge false equivalence in OP's post.
To add to this, another reason Oldbag isn't as hated as Hotti is because her flirting with grown men isn't her only joke, or even her principal character trait. The main joke with Oldbag is that she's an egotistical, old school woman prone to long-ramblings who, despite her inflated sense of self-importance, is more often harmful than helpful, and nowhere near on the moral high ground compared to others as she thinks she is.
In other words, when Oldbag appears on screen, there are a number of different jokes you can expect. With Hotti there is one joke, which is either him creeping on a minor or him creeping on a woman in a vulnerable position. That's a part of what makes Hotti especially fucked up for me: it's not just that he fucking stalks Franziska and Ini Miney, but he does so when they're fucking injured and are in a place where they're trying to seek care. He's the fucking worst and is not funny at all. Wendy calling Edgeworth "Edgey-poo" is nowhere near on the same level.