Can you point to any team in the league that hasn't undergone significant core turnover in the last 3 years? Here's a reminder of some guys and where they played 3 years ago.
Horford and Kyrie were both Celtics, alongside Rozier and Morris. Dirk Nowitzki, Tony Parker and Vince Carter were still in the NBA. DeAndre Jordan was a Dallas Maverick. Andre Drummond was still in Detroit alongside Blake Griffin. The Warriors had their big 4. Melo and Chris Paul were Houston Rockets.
I could go on and on really. The fact of the matter is that the modern NBA is very very fluid.
For example, Marcus Smart is I think 11th in the competition when it comes to longest tenure with one team, behind Haslem, Curry, Mills, Beal, Lillard, Lowry, Zeller, Giannis, Gobert and Embiid.