Been kinda wondering that myself.
One thought is that they aren't being developed.
Another is that the talent isn't being used wisely in in-game situations.
Are we just missing on really talented recruits when they go straight to the bigs instead of coming to campus? (Are classes ranked before the MLB siphons off their prospects?)
I don't know the answer, but for all the hype around our recruiting classes, we aren't seeing what you'd expect on the field consistently.