Wentz, Darnold, Mariota, ... The miss rate is pretty high to pass on someone who's at least pretty good.
There's no guarantee the Saints luck out with a rookie QB. If Payton's record of drafting QBs is any indication of what to expect from rookie QBs, odds are they won't. And, if we go with a rookie and don't hit on one, we may very well wish we had a Ford Taurus 5 years down the road.