A top-15 pick should be an obvious upgrade immediately over a career third-stringer, full stop.
I won't let any anxieties about a pick that is exciting but has legitimate questions ignore that.
The 13th overall pick at QB is a massive resource investment and Simpson was picked to be the next franchise QB - NOT a backup QB.
Stetson Bennett is a 2023 4th-rounder who never showed enough to take the backup QB spot in the entire time he was here.
When you take a QB at 13, you're saying "this player is one of the best 13 prospects in the entire draft class at any position, even if he needs a year to sit." That implies NFL-ready traits — arm talent, accuracy, processing, pocket presence — at a level that should make a former 4th-round backup look like what he is. The Rams reportedly had Simpson as QB2 on their board behind only Mendoza. If that evaluation is right, Bennett shouldn't be in the same conversation even with time in the system (time he wasn't able to use to take the backup QB spot!)
If a top-15 investment can't beat out a career third-stringer in camp, it's a real signal that either the evaluation of Simpson was wrong or Simpson's development curve is far worse than should ever be expected for the kind of investment we made and therefore we should expect to continue looking for a future starting QB.