There were several things about that team that resulted in all the good passing. People tend to acknowledge the obvious, the pass itself. It all started with Bird, his vision and passing were unbelievable, and Walton too, others as well. But I don't think that is what made that team so good. What was really exceptional about that team was the off ball movement, the cutting, off ball picks. They didn't just stand around and watch the pick and role develop. Everyone was on the move and with purpose.
GSW are actually the closest thing these days, all driven by Curry. He is a great shooter, of course, maybe the best ever, but if you really watch him, he is like Gretzky. As soon as he passes the ball, he is cutting or curling, moving, all the time. A move ahead in his head.
That to me is where this Celtics team (and all teams) lags the old Celtics teams. That off ball movement isn't there. They don't have Larry Bird either, of course, but I don't really understand what happened to the purposeful, choreographed off ball movement.