In the 1980s:
The Top 10 Teams of the decade won 73% or more of their games (2 teams won 80% or more)
In the 1990s:
The Top 10 Teams won 75% or more of their games (5 teams won 80% or more)
In the 2000s:
The Top 10 Teams won 73% or more of their games (4 teams won 80% or more)
In the 2010s:
The Top 10 Teams won 73% or more of their games (5 teams won 80% or more)
It would be abundantly difficult to argue that "talent" has been any more, or any less, dispersed from any one decade to the other - or that the dominant teams of any of those eras were any more or less dominant than those of any other era.
The Big Dogs may change, but the margin between Big and Little Dog remains the same.
Win percentage computation form (stassen.com)