No coach on a bad team is secure enough in his job to be mediocre to bad for years. Either way, that coach is fired. Might as well be fired after taking a risk.It's all about timing and going all in now only to fail sets the team back 3 years minimum. You do need to pull the trigger at some point but is it the right time? IMO the better move is a reasonable 3 year deal with a veteran not happy with their current team and save the draft picks for support roles in the trenches like offensive line.
If you're the coach you want to tread above water and keep your job until you can find your guy. If you go all in on a bad QB field you're probably going to be looking for a new job by the end of the year.
Plus, if you bring in a decent veteran QB, you'll be picking in the 10-20 range. If there are good QBs in later drafts, you'll have to either trade up to get them, or hope there are a least 3 or 4 really good ones, so you can hopefully pick one up.