The narrative tries to paint the Darkling as this "nuanced antagonist" who might have had good intentions but has been corrupted by his age and power which rendered his methods immoral and cruel.
I suppose, Novokribrisk destruction was aimed at that goal: to show that he doesn't shy away from killing massive amounts of people to further his grand vision.
The retcon with Genya who claims she was apparently so valuable that the Darkling had to specifically manipulate her in order to make her stay in the palace and get raped is also very obviously to serve that purpose. By that time Bardugo was so desperate to enforce her "clever" vision that she had Zoya and Genya routinely break the fourth wall in order to verbalize this exact thought: "the evil Darkling doesn't care about individual lives as long as it helps him to achieve his eeeeevil mwhahaha goals!!!!"
And every time, every new claim is self-defeated by the four horsemen of atrocious writing: the authorial incompetence, ignorance, negligence and arrogance.
In order to create a chillingly ruthless villain/antagonist who has the point but tries to achieve it by monstrous means, their plans should be precise and strategically sound. You should see what king of logic they are following and notice that it does make a very twisted kind of sense. It *technically* works, but reveals a horrifying cost under closer inspection.
For example, there is a character who genuinely abhors violence and wants to reduce suffering in their country. So when she comes to power, she makes sure no criminal, no troublemaker is killed or imprisoned. And on surface, it works: violent crimes in the country are practically unheard of, everyone lives in peace and nobody rots in prison. But of you ask how she achieved it, you'll find out she has mind magic and routinely wipes the memory and erases the personality of every person who doesn't meet her standards, turning them into a docile, self-abiding, complacent citizen full of endless gratitude to her. She genuinely believes she is helping them.
You can see the fundamental goal of this character. You can see how in her mind what she does is righteous because it aligns with her ideology. You also can see, undoubtedly, that her methods are far more insidious and harmful than outright violence.
It doesn't work with the Darkling. We never learn about his actual plans and vision besides a few hysterical, vague lines like "he wants to take over the world! He'll never stop! He is evil! It's all about power!!!" as if they mean anything substantial. They are all told by their detractors, but we never see what exactly would be so bad if he took over or how it is supposed to be better with anyone else.
The "arguments" about him punishing traitors or trying to seize power ring hollow twice because a)that's how army and politics work b) the "heroes" do the same and far worse for lesser reasons and it's never addressed. And don't let me start on the alleged "master manipulator" status: neither manipulations themselves nor their effect are shown.
Worse than that, you clearly can see multiple opportunities for him to be the very monster and tyrant the narrative tries to portray him as, and every time he is inexplicably restrained and lenient.
Novokribrisk is too weak as a strategy because the reasons for destroying it are not clear while the flaws of this plan are glaringly obvious. Genya's conspiracy theory is even worse because it has more holes than a pasta strainer. Those strategies do not sound like they were conceived by a ruthless, seasoned general and strategist with the unfliching focus on success no matter the cost, they sound like they were written by a person who failed basic logic at school and couldn't be bothered to mull over their writing or consult someone whose political grasp exceeds that of a toddler.
Those deeds don't make you fascinated by their ruthless pragmatism and the callous dismissal of human cost. They make you scratch your head and ask what kind of idiot wrote that crap. They are supposed to prove the character's strategic genius but undermine that very claim by their sheer stupidity and irrationality.
That once again proves that the Darkling is not a well-written character. It's not nearly enough to "intend" to create "an antagonist that are not easily dismissed", you also need a skill for that. Aleksander is as poorly written as the rest of the books, but he has the potential that is mercilessly squandered by an unintelligent, hypocrticial, morally repugnant hideous little tale. I don't believe it was intentional, but I find it deeply ironic that the character who is labelled as "monster" and "villain" shows more decency and humanity that all the "good guys" in this story together.