Don’t get me wrong, Mal was a complete asshole in the books up until his 180 shift in R&R but at least then he had potential for a solid character arc. A lot of people disliked Mal in the books because he represented an all too common type of guy that, while not a serial killer, was still extremely unpleasant to deal with. His petulance and immaturity felt real and it felt fitting for a boy who had the sort of orphaned upbringing that he did. By no means did the books address this bad behaviour in a meaningful way, but the fact that it EXISTED could have been developed further for the show.
Except the show didn’t do shit. The writers of Shadow and Bone saw the Book!Mal backlash and went “Oh no! Everyone hates him so we better make him nicer in the adaptation!” But in doing so, they squandered the potential of his character arc and turned him into a boring, but nice boyfriend to Alina. I find the Malina relationship to be so boring and not compelling as it refuses to delve into any deeper emotional conflicts aside from fights that get resolved in under 2 minutes. Mal is so so nice and such a good boyfriend to Alina that it becomes all that he is. They even took out his conflict with Nikolai that was CLEARLY caused by his insecurity in his masculinity and traced it for an uneventful buddy-buddy relationship.
Mal is symbolic of the showrunner’s failure to develop the themes and characters of the books into a tv adaptation. Rather than seizing the opportunity to build upon the missed potential of the books, they choose to change superficial aspects of the story in an act of cowardice. Making Mal an asshole that would eventually develop into a good guy was too much of a risk, so they just made him boring.