What do you mean by "legit qb"? Top 5? Not realistic.
No matter how poor you think Tyrod is, he was the quarterback of the 10th most efficient offense in the NFL in 2016. One year after leading the 9th most efficient offense. The defense finished 26th in DVOA in 2016, one year after finishing 24th. The defense is the problem. And aside from having an elite quarterback like Rodgers or Brady, the team isn't going to be very good with such a poor defense.
So either the GM isn't doing his job and the players aren't good OR the coaching staff was to blame for the poor defense. If you think it's the latter, then McDermott and his staff should be able to greatly improve the D. So why would you not want to keep the offense the same?
It makes no logical sense to want to replace Taylor if you think the team around Taylor is good enough to realistically compete for a Wild Card right now.