They are not garbage. They work moderately well now, but only after you remove magic or physical armor from enemies. Depends on the kind of grenade and your build.
They are useful in a pinch, or when you ran out of other moves, to soften up enemy armor or deal damage and effects when they are out of armor. There isnt many to be found, those and the ones you craft can sell reasonably well if nothing else. Better one grenade than lugging around twenty buckets.
And thats about as it should be in a fantasy game of this kind.
