Bullock would make it somewhat competitive, but everyone denying Steve Bullock isn't a strong candidate for the general election is kidding him/herself. Sadly, he has no chance for the nomination, but if he were to the nominee, he would destroy Trump just like Joe Biden will.
He is a strong candidate, i agree (and i think few will deny it), but he's unlikely to win the nomination. And it's time for a Democrat who can pursue her / his ideals, and not a centrist candidate who will make the margin of victory bigger. Still, Bullock is a good guy, surely. Would vote for him as well (which i wouldn't do for Biden).