What makes for an interesting MC is very much personality-driven, and personality is not a replicable thing. Flows can be imitated, not so much the complete package of temperament + experience (and subsequently: worldview, identity, sense of humor, etc). If the skills are up to par, what a good rapper has achieved is conveying that personality to you, making you feel what he's about. Enthusiasm about a new rapper is less for me about "are they pushing the technical side of the craft" as much as "is this unique and making me feel something in a new/different way?"

(edit: not so concerned whether they lose it down the line, someone else will always pop up to hold my enthusiasm)