I agree, good/great players wanting the biggest payday possible and not being opposed to leaving this dumpster fire of an organization isn't really RonCrew's fault. That's why I'd never fault them for Scherff or Trent.
Cutting a decent starter on a reasonable salary just to "get younger" is a far graver offense. Compounded with Roullier's issues, it really stands out.
Basically, I think Scherff and Williams leaving were unavoidable and Roullier's recurring injuries were unforeseeable, while Moses leaving was completely avoidable.
I can see why people would blame it all on them, though. The OL has been ruined, and Cosmi is really the only high draft pick devoted to renewing it.
They thought they could fill the gaps with ex panthers and coach up late rounders. It hasn't panned out.