I’m gonna leave out stuff that isn’t his fault (the series giving him too much spotlight, some sections of the fanbase) and try to address things that are only about him:
I have pretty complex feelings about Nagito. As a character and antagonist, I like him, because he’s layered and interesting and cool to watch. I also respect his, um, tenaciousness (torturing himself in Case 5 definitely takes serious grit). But as a person, he hits a lot of my “grr” buttons. He shares the same mindset as HPA, that hope and talent are everything, which makes him a pretty big jerk. He’s so militant to his beliefs he’ll try to instigate murder for them and doesn’t seem to mind putting his classmates at risk. And at the end of the day, he refuses to grow or learn anything. Static characters are fine, but Nagito’s “talent is everything” mindset directly goes against everything the series has hammered in. Even characters like Jin and Izuru showed exception or grew out of it. Yet Nagito alone doesn’t change, and Nagito alone receives absolution for that.
…I’m also a pretty big Hajime fan, so Nagito’s treatment of him after Trial 4 really irked me.
So…yeah, I have some mixed feelings on the dude. I like him best when he’s antagonistic. I can take him in small doses when he’s a protagonist, especially when he’s actually trying to be nice. But putting up with him in a protagonist role for long periods, when his jerkishness comes out full-force and he’s still adhering to that unhealthy mindset? That’s more than I can handle.