Since Bird and Magic won titles as young pros in the early 80s, very few players have been the main guy on their team and won a title before age 27.
Using Finals MVP as a proxy for being the guy on a championship team (with a few exceptions like the Warriors first run):
Steph was 26 (didn’t win Finals MVP but obviously was the main star).
DWade was 24, but he also had a hobbling Shaq.
Duncan was 22 but had an aging superstar teammate and a well constructed team. Same with Kawhi.
Tony Parker was 24 when he won the Finals MVP, but it was obviously TD’s team.
Dumars was 25, but it was Zeke’s team, who was 27.
Then you have Magic and Bird who did it young.
Jordan, LBJ, Hakeem, Shaq, KD, Dirk, Zeke, all couldn’t win the big one until they were at least 27. Kobe didn’t do it without Shaq until he was 30.
So in the last 35 years, the only guys who were led their team to a title before age 27 were Steph, DWade, and the Spurs.