I don't ship Darklina not because it "romanticizes" or "glorifies" anything. I don't ship Darklina simply because it sucks ass.
It's not well-written at all. There is absolutely no build-up, no organic development to their "relationship," not even scenes between them that would indicate any romantic dynamic, but there are scenes that plainly contradict any development whatsoever.
The actual "romance" goes like this: the girl meets a guy, thinks he is a soulless monster, talks to him four times, shows zero interest in him as a person, gets kissed by him, which makes her wet, admits they are strangers and are not in love with each other, hears someone confirming her assumption about him being a soulless monster, runs away, and spends the rest of the books berating herself for still getting wet for him and blaming him for her hormonal outbursts (because heaven forbid a woman experience sexual attraction on her own volition, not in that puritanical fable! She must have been seduced, manipulated, tricked and led astray by the devil himself!)
Because Alina's puritanical hysteria is not "complex" and "nuanced", it is pathetic and off-putting. Because her weird Darkling-specific Madonna-whore complex (a monster/boy dichotomy) is genuinely creepy.
Because Aleksander casting pearls before that particular swine isn't cute either—it's baffling and frustrating. Because Alina as a person has the romantic potential of a dead flea-ridden rodent, and everything about her is unattractive, unappealing, and downright repulsive.
Because due to the poor (read non-existent) relationship development, even their "iconic" quotes ring hollow.
Because his "evilness" is told but not shown, and her nastiness is very much shown but is labeled as "goodness." It's not morally ambiguous; it's morally rancid.
Because their "likeness" is based on nothing but the fact they are both rare types of Grisha.
Because there is no genuine moment between them that wouldn't be marred by Alina's ignorant, bigoted, dehumanizing bullshit.
Because their relationship is interesting only as long as you don't familiarize yourself with the source material: the concept is there, but the execution is dreadful.
Darklina IS a problematic ship. The problem in question is shit writing.