Increased pace is making the best teams a lot younger. This is the least experienced top 4 teams the league has ever had.
The Thunder, Spurs, Pistons, and Celtics all have an average roster experience of 4.5-5 years.
The only way to explain this is the increased pace, and just as important, the increased mileage from closing out 3 pointers on defense.
This combination of having more possessions and having to move more during them has made older players a lot less effective unless they are ex All-NBA level.
EDIT: Here is the visual for the last 45 years of Pace vs Experience https://imgur.com/a/uSpsQl6
You can see the most experienced teams all came during the Dead Ball Era.
EDIT 2: This is all weighted by minutes played. The average experience any player on the court at any given time during the 2011 Mavs season was 10 years.