I think the first team is easy. Second team is a lot harder.
Tatum: 8 seasons (not counting 2025-2026 to this point), 6 All Star appearances and a championship
Brown: 10 seasons, 4 All Star appearances (and likely a fifth this year) and a championship
Pierce: 13 seasons (cutting his first two years out because they were before the relevant time period), 10 All Star appearances and a championship
Garnett: 6 seasons, 5 All Star appearances and a championship
Rondo: 7.5 seasons, 4 All Star appearances and a championship
Those are my first team locks.
Ray: 4.5 seasons, 3 All Star appearances and a championship
Horford: 7 seasons across two stints, 1 All Star appearance and a championship - I view Al as a mercenary tbh but it's very hard to argue him out of his spot here
Second team locks.
With the last three spots, I'm taking Smart, White, and IT.
Antoine Walker is an odd case because the relevant time frame cuts out four of his seasons and one of his All Star appearances. I don't think his contributions after 2000 (three years and two All Star appearances) merit inclusion on the second team over IT, whose MVP-caliber season stands above anything Toine (or any of the remaining fringe candidates) did in this quarter century.
KP, Jrue, Kyrie, and Kemba weren't here long enough to get much consideration - two years each. Nobody else from the 2000s stands out to me. Ricky Davis? Young Al Jefferson? Nah.
For the record, I do acknowledge that I'm giving All Star appearances more weight than they deserve but they made the back-of-napkin math simple.