I think you're missing the reason why people are excited about Black Panther. It actually has more to do with the motivation of profit than representation. Obviously there have been several decades of positive black cinema but the audience for those movies was always intended to be strictly "urban". And their small budgets reflected the assumption that studios thought only a small subsection of America would be interested in a black movie.

Black panther proved for the first time that you could put $200m behind a movie with a predominantly black cast, market it to mainstream America and still make $1b in revenue. Marvel/Disney's primary motivation was still profit. There's no way they would've green-lighted(greenlit?) that movie if they thought they would lose money on it.

So it's not about representation just for representation's sake. But rather celebrating the fact that representation is no longer held back due to a lack of profit.