I don't think the game intend to "immerse" you with the world. Not with the amount of meta information currently given to you.
The only suggestion I can give is: Say no.
Wyll and Gale will approach you if you are goody two shoes, but once they rejected, they will not approach you.
They're adults, they can handle the "no" - and you can still progress with their quest.
I was going to say this same thing. Maybe it's because I'm a woman, but I'm terribly used to unwanted people insisting on flirting with me, and I just say no. In fact, some insist even when you tell them no, so in reality I see it as quite realistic and it doesn't spoil my immersion XD
Yea, I guess, it'S no wonder, it'S mostly men complaining here, because we women are sadly used to that in real life. At least Wyll and Gale get the hint (not Halsin though - he is the perfect despiction of a 'nice guy'). So if the game does one thing, maybe men playing it and are put off by the unwanted attention might think twice before hitting on a woman again, just because she is friendly

It's a way to teach a lesson to men, I guess, but I don't think BG3 should be a learning tool.
But yeah, men are more sensitive than women when it comes to the same sex relationships. It's not their fault though, it's in their biology. There have been studies made on the subject and the way a straight man's brains instinctively react to a picture of two men kissing isn't flattering. Doesn't mean it makes them hate gays, at least not the normal guys, but they can't help it if it feels uncomfortable and nothing in this world can change that which is deep in biology. We've got to just accept it and move on. Thus I don't act judgementally when I see guys complaining about things being forced on them (and I'm not saying you do either), because they have a right to do so and it doesn't make them bigots.
Games are supposed to be escapism, for women too, and if there is a good intentioned lesson included to normalize things that people might not be inherently used to, the way to do it is to show it in a normal light. Companions in BG3 doesn't seem to act normally, thus the apprehension. But I don't think any of it is intentional, it's just poor game design and people want Larian to fix it, rightfully so.
And lastly, if a game is supposed to be accessible to most anyone, then I think it should take in to consideration most of the people who are buying the game. I'd suspect that it's possible that players in BG3 might be close to 50/50 men and women, but about 99% of them are straight, or if we're being very very generous and take in to account only USA, and the supposed change in sexuality, even then the straight people make at least 92,5% of the player base and some of them are bound to be alienated by the same sex relations that the game is pushing, most likely unintentionally.
If we take in to account the 'openness' to new things factor, which again is about 50/50 in people, I'd say that about, at least, half of the men aren't going to be comfortable with the same sex approaches. That means at least 23-25% of the player base at minimum doesn't like it, which is more than double the people who might actually enjoy the same sex flirting. Ironically, unsatisfied people are much more than that, because many women don't want to be hit on by other women either, and I see no reason why gays would want women companions overly come on to them and vice versa for lesbians. So who are the romances for? Strictly bisexuals? How many of them are in the player base?
Obviously I'm not doing exact science here with my estimates of percentages, but they're pretty close to truth and I'm also not saying that a game needs to exclude anyone, in fact, I'm saying the exact opposite, and right now the game is kind of excluding most of it's player base. It won't stop people from enjoying the game, but it might stop them from enjoying romances, which I at least consider a major thing in today's RPG's.