To be fair, I think what they were going for is “sexing up” everyone in the Mirror Universe, which doesn’t really make it a whole lot better, because then the unfortunate message kinda becomes that being sexual and promiscuous equals evil and deviant. A sort of inadvertent slut shaming on a universe-wide level. And I guess their thinking was, since everyone is so sexual, some of them must be gay, too. In a way I bet they thought they were kinda edgy with this stuff, even if much of it feels like a teenage wet dream brought to the television screen.
But yes, I can totally see now how that aspect of the Mirror Universe is problematic. All of this likely flew right over my head when I watched this as a kid. But now as an adult I got to wonder how much of what they showed me formed some unconscious biased opinions about lesbian and gay people. It’s telling that the only time the writers felt free to include gay characters was when they visited a bizarro “evil” universe. Probably tells us more about them (and the mainstream view of LGBTQ+ people at that point) then they realized when producing these shows.