Very likely, in which case they definitely can be judged for their own irresponsible behavior and for failing to fix it. But not for failing to fix the irresponsible behavior of the guy(s) they’re having sex with.
Yeah, I don’t see how anyone could assume it’s a sexual partner’s responsibility to fix an addict whether they are themselves addicts (statistically very likely) or not. Also OP ‘didn’t want to go into details’ but it seemed this addict’s sexual behavior was more like obsessive auto-erotic than being with real women.
There certainly are sex partners who positively contribute to addicts’ problems, trying to drag them back down into it when the addict tries to climb out, for the partner’s own selfish reasons. But you can’t assume it’s the case with every addict who has a romantic partner.