Obviously I am not implying players in the 1960s were as athletic or skilled as those today. I only do this based on comparisons with peers.Remind me what happened following that "year after Russell retired". They took 1st place in their division 5 out of the next 6 years and won two more championships.
Stacked teams? If you were 6'2 and could dribble without looking at the ball you made an NBA team in the 50s and early 60s. If you could dribble with both hands you were burned at the stake for being a witch.