There's going to be a rather big drop off from Drew Brees to whoever replaces him regardless. Don't see the big difference between Taysom starting or a rookie/1st year QB out of the draft starting once Brees leaves. Especially not at the draft position the Saints find them in every year (late 20s, early 30s).
They can pay to keep Taysom and still draft a QB in case it doesn't work out. Doesn't have to be one or the other.
It's no different than what any other team goes through when they swing (and potentially miss) on draft and FA QBs.
Going from the all time passing leader and future Hall of Famer to literally anyone else is going to be a drop off in results and production. It's inevitable.
The good thing about Taysom is, even if he ends up trash as a starting QB, the Saints can still get their $$$'s worth out of him by lining him up at receiver, special teams, and wherever else... While most other teams are forced to bench their failed QB projects and that's that.
This whole "the franchise is doomed if they pick Hill" point of view seems like a massive overreaction to me.. especially considering how easy it seems to be to maneuver contracts and cap numbers in a team's favor if need be.
For the Saints specifically, say Hill's a bust? What's the backup plan? There's no stud QB the Saints are passing up on to choose Hill... So even if he fails, whoever replaces him is literally a gamble anyways. Just gotta hope for the best at that point.
Maybe if they were top 10 in the draft.. but the Saints don't ever have picks like that.