"Why would Alina choose Mal"
Because she LOVES HIM. NEXT.
"Why would she give up her powers?"
Because she didn't want them.
"She could have been The Queen! With Nikolai"
The queen said no thank you I don't want it without Mal!
Because she loves him! He's her bestie. She wouldn't willingly hurt him or choose that path if she were not narratively forced into that role.
Tormented and manipulated her.
"But they were made for each other!"
As narrative foils. He's what she fears becoming. He's her archenemy. She hates him. And this wasn't an enemies to lovers trope.
MAL WAS ACTUALLY MADE FOR ALINA IN A MORE FULFILLING WAY... he was there to support her, not oppose her.
"...Because Mal and Alina were only drawn together by magic"
Oh, because she and the Darkling were only drawn together because of normal circumstances? He didn't come abduxt her to use her as a pawn? I thought you just said they were fated to be together because of their magical natures. But when Mal and Alina have an unknown magical connection on top of a decade of friendship and care... you don't like it?
If you wanted some kind of dark romance, go read another book. Alina wants LIGHT in her life.