@DarkwolfX37TL;DR:
"Character flaws are okay because he didn't actually mess up."
Everything about Gohan, from his character design to his personality is trash. He's not a scholar, he's not a fighter, and he's not anything beyond saiyan fodder to keep his rabid fanbase happy.
Goten has better character development and his involvement can be summed up as "He's Goku's kid and exists sometimes." At least being absent is better than having negative traits associated with your unlikable character. He's set up like some ultimately relatable dude for all of the fans, but he fails on
both the human
and saiyan aspects of his personality. The full-bloods may not be relatable, but they're likable and represent the dream of always being able to surpass your own limits. Gohan is a failure in every respect; he's far too saiyan in terms of power and attitude to be humanlike at all and he also has no aspirations to speak of do e can't even properly reflect the human love of self-improvement and surpassing all odds. He gets everything handed to him and
still can't even use it properly. He's just some arrogant dude who gets creamed like a potato whenever he gets into a real fight. He
can't contribute to the cast because he lacks the drive of a saiyan, lacks the personality of a human, has the price of a saiyan, and has the incompetence of a human. Gohan has always been trash and always will be.