I mean Thancred spends most of the time being a ladies man and little else, then spends two and a half expansions being gone and then emo until he finally becomes more of a real character half-way through Shadowbringers.
I am simplifying a bit but that's in effect what happens there's really not much else to him outside of that.
Alphinaud has probably gotten the most character development out of anyone, altho I'd agree to some extent about Y'shtola I think she hasn't really gotten much development.
Urianger I'd say has gotten a fair bit of development tho and I do think his character just improves the further into the game you get.
But I don't think this is an issue with the female characters especially.
Alisaie has opened up a lot she still has the '' strong '' exterior but I think that's only looking at it surface level.
Most of her temparment has to do with the sibling thing with Alphinaud.
They added a lot more depth to her from Heavensward to Shadowbringers.
I also think that Yugiri has been developed a lot too, you learn so much more about her in Stormblood and see more sides of her and she has some really great scenes.
Yotsuyu is also the biggest highlight of Stormblood imo, and I thought Ryne in Shadowbringers was great I'd say she and Thancred sorta went hand in hand in their development tho.
I'd even say that Nanamo has grown a lot she has become far more pragmatic, her and Raubahn's arc were also one of the highlights of Stormblood imo.
Fordola I'd say is also more in the process of it too I don't think her character is done but we've seen hints of it.
But this kinda just makes my argument too because Lyse has received far more development and grown significantly in comparison to a lot of the other characters male characters included.
And a lot of the people hating on her seems to have wanted her to just remain a comedic punchbag which contradicts that argument.
I think that in the post story in particular she really steps up big time and shows that she is a very capable leader and understands what steps needs to be taken.
And she's also humble to the fact that it's not just about what she wants but what the people want.
Her character arc is pretty comparable to Alphinaud imo in the sense that she kinda '' grows up ''.
And people hated Alphinaud in ARR too, but it's like they just ignored/ missed Lyse's growth.
Edit: Oh yeah and Ysayle.
I'd definitely say that she got significantly more character development than basically any male character outside of Alphinaud in Heavensward...