Rendon did have a top 6 MVP year at age 24, but his others were at ages 27 & 29.
Devers started in the igs at age 20, and he came up through the system playing against pitchers much older than him. His break out year was at age 22 (2019) when he hit .916. Rendon's was at age 24, but his OPS was only .824. He then hit .765 the next 2 seasons combined at ages 25 & 26)
If you comp their corresponding age numbers (Ages 23-25):
.768 Rendon
.882 Devers
I know you mentioned Devers has "yet to break" the top 6, he's not yet 27. He has a .895 OPS since 2019.
It should be noted, Rendon was superb from ages 27-30 (.949 OPS), but he has dropped off the last 2 years: .724 from 2021 to 2022 (just 414 PAs). He's at .791 since 2020. At his age, that's amazing.
TOPS OPS since 2019
1.072 Trout
.981 Soto
.965 Tatis
.959 Harper
.943 Alvarez
.937 Judge
.937 Freeman
.928 Springer
.924 Acuna
.903 Betts
.900 Rendon
.898 Cruz
.895 Devers
He's a top 5 generational talent, and his defense is improving.