There's also the factor that "low self-confidence" is often used in bad writing as a cop-out flaw "since there has to be one", one of those Mary Sue classics, and overcoming it as a main thing feels intrinsically unearned. It's the game/story/medium telling us "she's actually already awesome, she just has to realise how awesome she is". That's nothing, and doesn't feel like real development.
And then if one pairs that with the character having real tangible flaws that the player/reader/audience perceives but the story brushes over because the character needs to be praised instead, it becomes doubly frustrating.
People have been listing actual flaws they found with Wuk Lamat in various places, for example the fact that until the game she didn't bother to learn about the country she wants to rule over and yet feels entitled to the throne, her stubborn naivety born from a spoiled lifestyle while refusing to look complex realities in the eye, her lack of empathy for her closest family members, her superficial solution attempts to everything, her addiction to the spotlight and what have you. Had they been treated as the serious flaws they are and made a point of causing her trouble, and her seriously reflecting and changing her ways, backsliding here and there, getting frustrated herself at the tangible flaws, and then grown into a more mature person gradually within her own limits, it would have done wonders. Instead, the game taught us that she just had to get more confident, because she's already great and everyone will grow to love her. That's simply poor writing and will sour large parts of the audience on the character.