up with other players to be considered tier 1.

For example, win shares/48 minutes. Duncan has five of the top 250 seasons (#90, 113, 116, 133, and 218). Lebron James has nine in the top 250 and 4 of the top 13. Jordan has 10 in the top 250 including 6 of the top 31. Duncan isn't close to tier 1 in this.

In comparison to some other players:
-Jokic is about to finish his 4th in the top 250 with 2 of those higher than any season by Duncan.
-Garnett has five in the top 250 (#47, 65, 120, 147, 244).
-Karl Malone has 10 in the top 250 with 2 higher than any season by Duncan.
-Anthony Davis has 4 of the top 250 with 1 higher than any season by Duncan.
-Barkley five in the top 250 with 2 higher than any season by Duncan.
-Rudy Gobert has 4 of the top 250 with 2 higher than any season by Duncan.
-Shaq has 7 in the top 250 with 2 higher than any season by Duncan.
-David Robinson has 10 in the top 250 with 7 better than any season by Duncan.
-Giannis has 4 of the top 250 with 3 better than any season by Duncan.

Top 250 seasons in BPM
-Duncan 5 top 250 seasons with highest at #79
-Lebron 18 top 250 seasons with 10 better than Duncan's highest
-Jordan 11 top 250 seasons with 9 better than Duncan's highest
So not really close to tier 1

Others
-Malone 8 top 250
-Barkley 8 top 250
-Giannis 6 top 250
-Garnett 7 top 250
-Jokic 6 top 250
-Anthony Davis 4 top 250
-Shaq 7 top 250
-David Robinson 9 top 250

In career BPM - Duncan is #16 all time with this group all pretty close (in order Barkley, A. Davis, Giannis, Duncan, Garnett, Shaq, Malone). David Robinson is #4 all time. Jordan and James are the top 2.

Career win shares - Duncan is #7 all time and is essentially equal with Dirk. Duncan falls in this group in order (Malone, Duncan, Dirk, Garnett, Shaq, D. Robinson, Barkley).

Top 250 VORP seasons
-Duncan with 5 (highest is #52)
-Jordan with 11 (9 higher than Duncan's best)
-James with 15 (8 higher than Duncan's best)

My post is already too long, but in general looking at seasons this way shows some people are generally perceived too high because of titles (Duncan, Bryant, Olajuwon, Thomas) and players with fewer titles or none at all are comparatively underrated (Robinson, Barkley, Malone, Garnett, McGrady, Stockton, Paul)