Well, let me be clear on one point, Martin does a much, much better job than most fantasy writers. However, he made certain choices which hobbled him, and which hobbles the fantasy genre in general.
Here’s the crux of the issue–the generic fantasy world which has been employed in the vast majority of fiction is fundamentally misogynistic. It is a world where men play king and are important characters, well rounded and full of complex thoughts, and women are background characters, relegated to the sidelines. Martin, thankfully, attempts to usurp this system, but he only does it in one way, and that one way isn’t particularly flattering.
Here’s the general progression of Martin’s female characters–they usually start out as the queen character–impotent and weak, and as they develop, the only direction they seem to grow, as they become more active and complex, is in the masculine direction. In the end, the old trope is still in play–the only way a woman in fantasy can be an interesting character is if she pretends to be and behaves like a man.
This approach, in the end, keeps the same system cemented in place. The women become strong only because they play by the patriarchy’s rules. Are they stronger than usual? They sure are. But women should be able to be strong characters without having to become like men in the process–that’s just as misogynistic as the system itself.