Moore is the classic example of the backup QB that can come in a pinch and do an effective job filling in. But when the pressure is on and he has to carry a team from the beginning of a season to the end, he crumbles. Most backups in the league are this, and it's why they are backups. Chris Redman, Doug Johnson, Joey Harrington, Tony Banks, Charlie Batch, Byron Leftwich, etc. are all these types of QBs.
This is what happened in Carolina, and thus caused the Panthers to put most of their eggs in that basket. At most, there are really only 10-15 guys that are truly capable of shouldering the load of being the starting QB from day one.
You can certainly argue that Orton is also in this group, but he's arguably at the pinnacle of this group so it makes it look like he's with the next group up, which are the guys that are comfortable handling the starting job, but aren't going to be guys that rise to the occasion like in the playoffs to carry their team to victory.
"Vincere scis, Hannibal, victoria uti nescis" -- Maharbal, 216 B.C.E.