I guess every one of us hears what we want to hear. I hear Taylor is not a good enough quarterback to lead this team to the next level. He is part of the problem, not part of the solution. He is mediocre at best. I don't hear or see people saying he is the sole reason the team doesn't make the playoffs, that's your narrative.
To answer your question...yes, I do think that the Bills would be better off with one of the QBs you've listed. Would I want the team mortgaged to one of them for the next 5 years? I'd take a flyer on Keenum but pass on the others. The Bills will find their "future" QB in the draft (one of these years).