Not him, but it's not that he doesn't take it seriously, because he does take it seriously, it's just entirely his refusal to fight and when he does want to fight because he gets overwhelming power, he gets a high off of it and becomes cocky and that's a bigger downfall.
Gohan was always a docile Goku with Vegeta buried. If that makes any sense. The real problem I feel with Gohan isn't even that, it's just writing. He should never have lost all of his massive power, training or not in just a couple years, he never did during the 7 year gap after Cell, at least not to such a ridiculous degree. His problem is that he just doesn't need to be there, it's not his place, not his thing. Most of the characters have grown in their own ways by growing up and settling down. Goku and Vegeta are the only two that really thrive off of it and because they're full blooded Saiyans and they stay young far longer.
But I will say this. F. Trunks is the development Gohan should have gotten. Someone who doesn't want to fight, but is going to to protect people, and won't beat around the bush when it comes to killing and ended it, or trying to.