Why is fantasy literature bad at writing women?

I’ve read a fair deal of fantasy literature in my time and one recurring problem I’ve noticed is how poorly female characters tend to be written. WOT series is a big one with this.

They’re usually written one dimensional and are there as either for male fan service or as a romantic partner. Rarely are they fleshed out and treated as well developed characters themselves. It does happen (Eowyn in lotr) but it’s definitely not the norm.

Is this because the writers just don’t know how to write women well?

Why is fantasy literature bad at writing women?
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