Producers have a certain style. Just because you can pick their beat doesn't make it bad.
Just Blaze has a vey distinctive style, Johnny J has a distinctive style. Dre does, but does change it up occasionally. And Lil' Jon is distinctive as he uses a dance music sampler, and he's the only one in hip-hop who does. Plus he shouts all over them.
As for him doing a lot of beats yeah, maybe he will get overkill. But he's hot, everyone wants a Storch beat. If someone offers you 50K for a beat of a cd you've sent them. You gonna say no?