Yeah, to be fair:

Attacking roles: Covered by Auron, Wakka and magically by Lulu. Seriously, Lulu is freaking powerful

Defensive/healing: Yuna mainly, Wakka's status ailments do come on handy

Supportive: Yuna and Tidus, hell, even Rikku's mix is very supportive based


This doesn't leave Kimahri with much to capitalise on because everyone sort of fills a role anyway. However, steal and use is only available traditionally by just one character: Rikku. She at the beginning is incredibly fragile. Kimahri has the initial defence and HP boosts from his centre portion of the grid, alongside Rikku's initial HP boosts in her first "circle" area (I counted like three or four in just that short sphere) so he is alot sturdier. Sure, his attack goes down the pan, but then that's why you have Auron, Lulu and Wakka when you don't need stealing or use.