He's still a top 20-25 MC, you just have to put the latter part of his career in the proper perspective.
He's not the most interesting cat to listen to but his consistency is remarkable, i'd still call him a top 20-25 emcee, you just have to put his career in the proper perspective.
His overall legacy is unquestionable though, regardless of how you feel about his material post/whatever. Not everything is for or about YOU.
Mos Def is someone who's legacy is kinda in purgatory, shyt com even seems more visible on the acting tip than him despite not being as good of an actor.