Honestly, up until Shadowbringers I never really considered Hydaelyn to be much more than a convenient plot device for the Warrior of Light's power. The reveal that Hydaelyn was, in fact, a Primal was quite intriguing to me.
My own approach is to split characters into one of three categories - namely protagonists, antagonists and villains. I only really care for the first two, as outright villains are just as boring to me as goody-two shoes who can never do any wrong ever. For me, it's about understanding the 'why' the various characters do that they do.
I also like the underdogs. I have a soft spot for Pureblood Garleans, for instance, because the idea of a race being unable to manipulate aether in a setting heavily reliant on it is pretty neat in my view. With that said, it's only the likes of Regula, Varis and Gaius that I root for. They're varying shades of grey and thus firmly 'antagonists' in my eyes. Whereas the likes of Valens and Zenos...have zero redeeming qualities and thus are, sadly, rather one note villains.
Though with that said, I don't consider villains with no redeeming qualities to always be terrible. Valens, as horrible as he was, didn't overstay his welcome and had some amusing scenes whereas Zenos lost me after far too many cutscenes of stagnant behaviour.
My taste in characters is pretty broad, I reckon. Aside from being fond of Regula, Varis and Gaius...I also quite like Fordola, Thancred, Y'shtola, Hien and Magnai...amongst others.
That extends to the Final Fantasy series as a whole. I'm just a whole lot more invested in the likes of Gabranth, Seifer, Edea, Beatrix, Cloud, Vincent and Larsa. So, yeah, Venat/Hydaelyn has the opportunity to change my opinion depending on where things go next.
I don't know if that clears things up, but it's getting late so I should probably sleep soon! Apologies if it's a bit rambly!