If you were asking this in 2016 then I think Sean would have a better argument for being included, but he didn't really do anything big (no pun intended) those last couple years.
Meek really didn't make much of a lasting impact. Dating Nicki and beefing with Drake are his career highlights at this point.
Ross peaked in 2010. If he had continued through the decade on that Teflon Don level or better he would be a 2010's legend, but after GFID i really haven't seen much hype or impact from his albums. Seems like rap to a backseat to his businesses.
Nicki's third album was Curtis status. Multiple singles that went nowhere. Weak album. She can rap but doesn't have the catalog to back it up.
Future probably has the best argument for it. He was there throughout the entire decade and made a lasting impact.
Travis Scott could be argued too but I feel like you don't get Travis Scott without Future. He also has less charisma than everyone else mentioned imo