Everyone was useless by the same metric.
Except for Goku, obviously.
I dunno
Piccolo manages to stay relevant in every arc, and the side characters go through varying amounts of usefulnesss (like Gohan and Trunks). Goku didn't even beat Cell!
Vegeta was truly useless after the Namek saga though. No scratch that, the Prince of All Jobbers was outright detrimental. (He's the reason Cell and Buu managed to go as far as they did)