Why does a degenerate series like this have better character writing then the other crap :O Like look its an MC being a real person and acting like a real person :O
The character writing's pretty shit, really. He doesn't act like a real person, he acts like a Protagonist™. Every single thing that happens or that he does he just rolls with it with complete aplomb and does/says/knows the exact right thing on how to handle it. He has barely any personality beyond "Oh I'll cheerfully handle this situation entirely to my advantage". He doesn't display any real drive or motivation, he's presented with issues and he solves them seemingly just to resolve the issues.
"This girl's in trouble, marry her."
"Okay."
"This girl's traumatized."
"I'll fix it."
"The water sucks."
"The water's fixed."
The closest he's come to having a genuinely emotional reaction was when he got slightly pissed at his brother, but the fact that he knew exactly what to say and do to cut said brother down to size without provoking an immediate reaction that would have negative consequences just goes to show that beyond his ability to read grimoires, his real isekai cheat ability is being the author's self-insert.