Too many are underrating Duncan and the hallmarks of consistency, flexibility and and longevity. And overrating players that had 2-3 years of elite performance followed by nothing special, or that did nothing but defense and spent no effort on the other side of the court. Or that ultimately were great at one or two skills at defense but failed at the whole picture.
Duncan's advanced metrics for the first 10 years of his career are amazing. And during this time, he won 4 les as THE defensive anchor and team leader. So many others mention great defenders for a few years that may have one ring. The prime Duncan Spurs are the best defensive team of all time, maybe not in a single season but for the entire stretch overall. It's like comparing Hakeem to Duncan. Duncan wins because of consistency and longevity. You get credit for adjusting your game and staying elite.
In the the years that have followed, Duncan has had a slow decline but has maintained his role as the defensive anchor and adjusted his game to maximize the strengths he retained. He is still the center of the defense at the age of 38.