If a game is to be truly successful, then the classic tropes need to be present and at the forefront. Those who enjoy niche tropes tend to be very vocal about their preferences, though it does not really translate into engagement.
Deliberate subversion has become very boring. I do not want the classic male knight in shining armour to be cast aside in favour of a character like Karlach. You can make a point that both could be available as companions as a compromise and I'd begrudgingly agree, though if such things come at the complete expense of the classic tropes? Then no, thank you.
I could be wrong, but I think, BG3 was mildly successful despite not having the male white knight in shining armor

And Karlach somewhat of a fan favourite, so I think this supposed 'niche' worked out quite well for Larian. Hopefully it makes them more comfortable in going different ways.