Yeah, making the target a whiny brat is detrimental to the game on many levels.
- He doesn't deserve getting fucked by either the villainess or the heroine.
- He isn't worth saving.
- He doesn't have virtues to get destroyed in the first place, so the corruption won't change him noticable.
Most corruption storys that focus on a younger, male person, emphasize how that boy is "pure", as in kind, naive, well behaved, responsible, studious. Usually he has a very positive relationship with the heroine. All this is build up so that the corruption and fall make it more so devastating, because all these virtues are removed and turned into sins. His devotion to his mother, which is virtuous, is directed toward the villainess, so its now twisted and wrong. He fails his studys, his career and social life which he used to manage splendidly, because the corruption twisted him that much that he abandons it.
I get that it would be the wrong approach to make the son a chad, then he wouldn't have a reason to fall for her (or it wouldn't impact him as he is used getting pussy), but a whiny loser on the other side of the spectrum is just as bad. Make him a kind guy with a very good relationship to his mother to contrast it with the bitchy cougar whos goal it is to destroy that bond.