I think the appeal of Carson Beck is 1) he is on a high ranked team and 2) high QBR. But that is because he is clearly asked to do less to carry the offense than either Mendoza or Simpson.
Mendoza
1,423 yards. 17 TD. 2 INT. QBR 84.6
Simpson
1,678 yards. 16 TD 1 INT. QBR 81.5
Beck
1,213 yards. 11 TD. 3 INT. QBR 84.9