Duncan is clearly tier 1, I would rank him #2 behind Jordan. You may laugh at this now, but when Spurs goes ringless for two more decades, they will realize how special Duncan really was.
Look at the Spurs franchise that stole so much credit from him, tiny budget, trash tier city for free agents, overrated coach, Duncan got 5 rings with weakest supporting cast and lowest budget (relative to rest of the league) to ever win even 3 rings. Just count David, Kawhi, Tony, and Manu's all-NBA appearances when they played with Duncan. Because of this trash roster he never repeated, and he did so much dirty work on the floor that doesn't give him stats.
Imagine if he had Shaq or Kobe (I laugh at any comparison of Duncan vs them, imagine LeBron went 2:3 vs Durant + Curry) Curry's roster budget or LeGM's teammates. LeBron is the most calculated star in NBA history. Incredible career planning, GOAT body (partly because he shrewdly avoids any dirty work that doesn't give stats), but not a team player at all, played in the weak East, stacked roster after roster, still only 4 rings.
Curry and Durant are both in David Robinson's tier in terms of overall impact. Joker is already in that tier, he has the best chance to make it top 10 barring injuries.