I don't think so because we've actually had players play over their head or have some sort of renaissance. Look at Belliard and Young last year, Lannan and Redding this year and last, Loaiza in 2005, etc. There are plenty of examples of players playing over their head.
I think the problem is consistency. The closest things to consistently reliable players we've had in this organization are Nick Johnson and Jon Rauch. Yeah, I know NJ missed a year, but that was due to a freak injury. Cordero was considered such before this year.
The Nats are having serious problems with setting themselves up at a position and not having to worry about it for a while. That's supposed to be an earmark of "the plan" - filling positional voids for years and years and complementing those centerpieces with necessary acquisitions.