For someone that says "steriods are the finishing touch," hahaha. It's a combination of a lot of things like others have said, but steriods are very important to your physique. The definition of good genetics to me, is shape and response, that's it.
Don't need good genetics to become pro though, there are a lot of examples, but the genetic freaks usually do well, Wheeler, Levrone, Ronnie, Ray, etc...