I'm not sure where this scorn for Vernon Carey comes from, but it's not particularly reasonable. When Carey was on the field, he did alright. Not bad, not good, alright. It's not anywhere near rare for an O-linemen to not start his first season.
Wannstedt for whatever reason did not play him. Last time I checked, Dave Wannstedt no longer is an NFL coach, and this is directly as a result of his inability to properly analyze talent.