I mean it would defo be nicer if this was the case but to me it seems that the author has made him quite a self centred character so he doesn't actually care about what people say which is why he doesn't listen. I feel like that is why the very first thing we are shown of him is him deliberately ignoring dead yooseung(?) saying he's sad. But tbh u guys' theories make sense too, and i have no clue the direction this manhwa is going so maybe its both even

I'm starting to think Geonpil (ML) had a selective hearing or some kind of head injury or something, he always seemingly ignore what other talking about even if it's talking TO him or he had ringing in his ears that he can't hear
I can't decide if this is purely a personality trait or a real disorder he had cuz it's been happening frequently enough to make me think this. Either way I keep find it fascinating regardless if it's a disorder or not, because his inability to listen to those around him when it's important ultimately is his own downfall