Thompson, Rieder and Bassett have all made the step up and have proven themselves to be Premiership quality. Bassett, despite losing form since, played a non-cap game for England not so long ago and Thompson was being mentioned in terms of the senior England squad at one point. No-one since though.
I guess if the academy structure is working the way the RFU would ideally like, then the top talent should be being identified at a young age and brought through the Premiership academy squads, only being loaned to Championship sides as part of that development. It may be that the effect of that is to widen the gap between the Prem and Championship, or the gap is being bridged by loaned players.