Sometimes you're just born in the wrong era. Pre-streaming, if you weren't Denzel, Will, Wesley (for the "limited" star roles) or Sam Jack, Morgan, or Laurence (for the old man/wise sage roles), they were either offloading your parts to rappers (see: early 2000s) or the roles themselves were so basic and one note (i.e. GotG) that they weren't going to pay you much for that. Furthermore, tv wasn't as respected so the options were even more limited.
Basically left you with the low budget Tyler Perry/Morris Chestnut "relationship" movies, or the usual black trauma porn focused on slavery, civil rights, or hood/gang warfare. Between Amistad, Blood Diamond, Gladitator, you can kinda see where Djimon was placed.
Nowadays tho, it's still far from perhect however, an Aaron Pierre, Mamoudou Athie, Damson Idris etc can earn lead roles in streaming programs (or a conventional cable show) and propel that into lead roles in big budget IPs with Disney, Pixar, WB, etc. Aldis Hodge and Idris Elba have more diversified opportunities now, particularly as leads, compared to 10-15 years ago.