I would say that the situation is very different for each. I feel that Doc was able to squeeze the most out of the veteran talent that he had and field a championship squad. And that is a great accomplishment but you have to realize that he had a LOT more to work with talent-wise than Brad Stevens does.
I feel that Brad is the right coach at the right time for this team. We are in a rebuilding mode and we have a lot of young guys. Right now, Brad is having to do more with less. But he is also a teacher, and will be able to work better to draw out the talent and develop the youngsters that we have. With a coach like Doc whose job depended on going deep into the playoffs, he could not afford to develop young guys like Sully, KO, Smart, Young, etc.
Of course I expect Brad Stevens, given what he has to work with to get fewer wins. But in time, I believe he can grow into a great coach for us, and the players that we do keep will have benefitted from the system that he teaches. In any case it's an apples to oranges comparison so it's totally not fair. I believe that Brad Stevens is the right coach for the Celtics at this time and the best for our current situation.