First, very few people claim he is a franchise QB, rather he is the best option for the interim--until a franchise guy is found. Every QB currently available, with the exception of maybe Cousins, has issues; for example, with Romo it's age and injuries.
Regarding your stats, people can just as easily focus on specific games (Seattle) or parts of games and use it to support a case for keeping Taylor just as you did to argue against him.
From my perspective, I also think he is the best option to have for the next 2-3 years as the Bills look for a franchise guy (Hopefully they draft someone like Mohomes this year). I view Taylor much like A. Smith, someone who is good enough to get you to the playoffs as long as you have a top 10 D.
We'll find out what the Bills think soon enough.