I figure I'm beating a dead horse, but what the hell.
Much like black metal, grindcore isn't focused merely on technical proficiency. The best grind bands will set a mood and atmosphere that is intended to be a chaotic sonic assault on the mind and body. Bands like Nasum, Napalm Death, Pig Destroyer, Rotten Sound, Circle Of Dead Children, etc. are perfect examples of this. They aren't occupying themselves with instrumental masturbation, simply because they aren't concerned with that aspect of their music. The main focus of these bands is to create intense music that will affect the listener.
If you're saying that all grind bands lack talent, then you are essentially saying that any band/artist that doesn't flaunt their technical abilities to no end (black metal, doom/funeral doom bands, for instance) lack talent. Making a statement like that in a serious tone would make you a fucking dolt, and I think you've already accomplished that.