if it's that then ig maybe if the dance doesn't match the beat/energy of the song. because if like the song is high-energy but dance doesn't match or song is like slow/not that energetic and the dance is high-energy then that's a no
also the instrumental a.k.a. the beats & like not what's sung (vocals, rapping & backing vocals) . the instrumental version of the song can also make or break because sometimes i just listen to the instrumental versions of some songs.
Before I got into kpop, I didn't even think that was such a rare thing, but it somehow is! Personally, I don't think it's better or worse than an only boys or girls group, because this was always the norm to me.
I think overall they aren't that widely spread, at least when it comes to popularity. The main problem is probably that the fans love to make up rumors and this can get uncomfortable for the members, so maybe that's why many don't really want to make a coed group. Just look at what happens when a male and female idol collab sometimes...
What is one thing you really love about kpop as a whole that always pulls you back into the fandom?