Honestly I find some of the complaints about the romance system ridiculous. Harassment? You tell a companion 'no' and they move on, as far as I can remember, with the exception of

1. Lae'zel, who gives you a YOU WILL REGRET NOT SLEEPING WITH ME, which yeah is kind of a jerk thing to say...which in case you have not noticed, Githyankis in general are kind of an entire *race* of jerks, which makes sense given that in lore they're kind of rampaging space pirates when they aren't hunting down illithids.
2. Gale, who is the only person I had to explicitly reject the flirtatious option in dialogue twice. Maybe that was a bug, but quite frankly he comes across as so gentle in his flirting that to call it harassment seems absurd.

I guess some take your rejection better than others. Wyll actually seems so sad after you brutally shut down his "dance with me" flirting that I honestly laughed out loud.

As for innocent, well, I think that depends on what you mean by 'innocent'. Karlach actually seems pretty 'innocent' in many ways, to me. If what you mean by 'innocent' is 'sexually naive', well, these are all grown adults, it's unrealistic to expect them to be *totally* inexperienced. But still, I guess some of them could be more on that side?

1. Lae'zel comes from a culture where clearly the standards of flirting and relationships are different (the Gith'yanki seem to think that outright inter-partner violence is romantic.) Of all the characters though, I don't think I ever heard a line from her about previous partners, and I went pretty deep in the relationship with her. It could be that she's a totally lovestruck Gith falling head over heels for you. It would be hard to tell though.
2. Gale starts out blabbing about his ex-gf (yes yes, Gale, we get it, Oooooh Mystra was so great) but other than that strikes me as fairly innocent. He doesn't seem very "forward" with his flirting t all. But to be fair I have used him the least out of all the characters so maybe I am missing something.
3. Shadowheart is the servant of an evil goddess who outright encouraged her followers to treat intimacy as something fleeting so that they would not form lasting bonds with each other. But outside of that she does seem inexperienced on how normal relationships are supposed to work.
4. Astarion is, well, Astarion. He's clearly not meant to be 'innocent'
5. Karlach.....well, she's a big raging barbarian and definitely plays into the stereotype a bit. Barbarians like to fight and f[HAVE INTIMATE SEXUAL RELATIONSHIPS].
6. Wyll...actually I don't know how innocent he is. I thought Wyll was super boring so he's the only character who I have always shut down completely right away, without bothering to play along with his flirting for at least a little bit.

I do think the romance writing has some weirdness (SO many people seem to be okay with polyamory and like, without ONCE bringing it up, seem to expect you to be okay with it too). Plus just...well to be harsh, just low quality writing when it comes to romance in general. I maintain that while Larian has improved in their writing to the point where they can do good character writing and make charming companions, they are actually still pretty bad at writing in general, and it shows in the romance.