That's not the case considering they're always finding new and interesting ways of using him. If Whis is going to be Goku's teacher, and Beerus potentially Vegeta's, why not have Gohan be the old Kai's ? Maybe have Piccolo find out about some elder Namakian he can train under as well. Vegeta may not be getting the big solo wins his fans want (I'm more than happy with what he's been getting), but there's no denying that he's one of the better utilized characters in modern DB, a treatment Gohan and Piccolo could greatly benefit from.
Of course he's still going to be used, but not in the same way Goku and Vegeta are. Sure he'll get to fight some henchmen here and there, but it's not the same as fighting the main villain of the arc. I want to make it clear that I'm not saying I expect him to be able to outright take down the main villain on his own, but he's the type of character who should be crucial to the overall victory. Gohan and Piccolo are among my favorites in Z, so it's very unfortunate to see them limited to low level tasks. Those should be left to the humans, not someone who beat Cell.
It was definitely a highlight for his character considering how he'd been written up to that point.