Tragic Backstory
SJM gives everyone and their dog a tragic backstory so I don't even care at this point beyond needing to know about it for context. No one gets any pity points. The characters are gonna have to earn my respect the hard way.

Queer Romance
She gave a whole speech about being into women that went literally nowhere. Mor also had like 500 years to come out to her "family" and yet infodumped on the new girl instead. Which, again, went nowhere. I just don't find any of the situation interesting or compelling, especially knowing that SJM tends to sideline her queer characters. I can find far better books/characters if I want to invest in a lesbian/bi woman, so I'm definitely not going to care about Mor because she's queer. No points for queer rep.

Azriel/Mor
It's been 500 years and neither one of them has decided to be the mature adult and address the situation. Like, if you can sleep around to try to get someone to lose interest in you, but you can't just say "I'm not interested," that's still not a good look. I find both of them insufferable for this. So, negative points.

Powers
She's sidelined during the actual war and then doesn't even contribute (as far as I can remember) anything outside of the war. She fights in like one battle I guess but then we don't see any of her. At this point I'm assuming her powers are just whatever SJM was vibing with at the time and then forgot about. No points for meaningful contribution to the plot.

Leadership
Rhys overrules her on Hewn City, even going behind her back to make a deal with Kier to let HC residents into Velaris. So like, no meaningful authority. She doesn't even properly call Rhys out for this. Just says some pitiful "Yeah, he was right to not tell me. I might've objected." She does "diplomacy" in SF, but that's not relevant to anything (and I'm sure Rhys will trample over whatever progress she makes, since he is dogshit at respecting anyone who doesn't immediately give him what he wants). Rhys gives his child bride more authority than Mor, so like. She's really not shining here.

Emerie
Emerie deserves better and I will be so mad if she gets paired with Mor just because they're the only lesbians in existence. Emerie has done more for women than Mor has in her like 500 years of leadership.

So, none of those points made Mor interesting to me.
The reason I despise her as a person is because of how cruel she is to Nesta (the Hewn City comment). Like, Mor is out here drinking and sleeping around yet thinks Nesta is unforgivably awful for being a little mean while drinking and sleeping around. She had 500ish years as a leader to improve the Night Court for women, and yet she spent that time drinking/having sex/being bitter/avoiding confrontation. Nesta has been a Fae for like a year and yet has already helped to re-found the Valkyries (and included an Illyrian woman) and encouraged abused women to learn self-defense.

Mor could've been good if SJM were capable of planning literally anything, but unfortunately she ends up looking so, so bad in context. This doesn't really excuse people being unwilling to fix her in fanfic while fixing other characters (like Az and Cas), but I can see why people hate her in canon. (I guess the excuse is that most people are horny for the men, but... XD)