Exactly. Outside of a very vocal group of sexist/racist people, I have yet to find proof that casting a black or female protagonist is something risky and revolutionary.
You still haven't explained why you think the Jedi were "forgotten" by the time of the OT. They are not mentioned, because why would they. But forgotten?
Well than name some big AAA films with huge budgets that feature black/female characters that don't come off as tokens who are sidekicks or are there for sex appeal. I think you will find it's very lopsided versus movies that have them as leads. Even Disney's own Marvel itself is self admittedly a huge offender of this.
Iron Man/War Machine: black sidekick
Captain America/Falcon: black sidekick
Black Widow: sex appeal
The entirety of the main core of the Avengers is white males who are the most powerful, and the Avengers is arguably the second largest movie franchise at the moment right behind Star Wars.
As far as proof look at any top ten/twenty grossing movie list the past few years from boxofficemojo and you'll find that hardly any of those movies have non white lead characters. Hell let's list off some from this year alone. I won't list em all cause cg movies don't count.
Jurassic World: No black characters and white male standard hero as lead.
Avengers:AoU: Already explained this
Hunger Games: I don't even know if there is a person that's not white in that entire series tbh
Furious 7: multi ethnic montage of a cast. the furious franchise is more of an exception than the rule
Hell I'll even list some of 2014's top grossing films
American Sniper: white male lead with mainly white characters
Captain America: same as Avengers, black sidekick, white male lead is the most powerful
Hunger Games: already explained, in fact in the prequels they probably made all the other people who had different skin color fight each other first which explains why almost everyone in the series is white.
Transormers: the main characters are cg robots and Mark Wahlberg
The Hobbit: no need to explain
Guardians of the Galaxy: white male lead
So it's racist pointing out that there are few/next to none big blockbuster movies that have a black males as the lead character or a female lead that doesn't focus on sex appeal? Or that most big blockbuster movies are predominately filled with white people? And ya know what, I'll even give comic book movies a pass since it's source material comes from stuff that was created in the 60s/70s.
There's been a weird gap for black actors emerging to make it big in Hollywood for a while other than Michael B.Jordan who just did his first big movie and his credits are pretty slim. Because Denzel, Foxx, and Smith have been slowing down for a while now.
Like I said earlier, is this due to franchise properties like Marvel, Tolkien, Hunger Games, Hobbit having primarily white characters due to their source material? Probably so, but I don't believe it excuses it entirely.
And it is revolutionary and risky having a black male lead and a female lead in this case, especially with her being white. Did you ever think that those two characters might have a romantic relationship in the future of the series? That's a pretty damn ballsy thing to do for a franchise as huge as Star Wars.