The purpose was two fold first to open up new rolls for minorities and secondly to make the movies more appealing to minorities. It was probably successful in both purposes. However, most audiences share your opinion. They generally don't like casting that totally disregards race in assigning actors to rolls. There have been a number of presentations where whites played black rolls. Generally black audiences had the same opinion. They don't like whites playing obvious black rolls.I have no problem with people who happen to be black and there are many black actors and actresses that I adore. Last night we again watched "The Pelican Brief" and I can't imagine anybody being cast in the role of Gray Grantham other than Denzel Washington though the role could have been played by anybody. But Denzel was perfect for the role. Morgan Freeman once said that the vast majority of all roles he has ever played could have been played by anybody. Of necessity he had to play a black man in "Driving Miss Daisy" and of course when he played Nelson Mandela in "Invictus."
But when they start remaking historical films with black actors replacing the actual non-black people who actually lived that history, it begins to become ridiculous. I suppose if there is a remake of "Moonstruck" they'll replace a lot of the Italian and Sicilian characters in Little Italy in New York with black actors which would be absolutely ridiculous. Or any of the cast of Memphis Belle replaced with black actors which would make it historically inaccurate?
The black characters in "Renaissance Man" however, given the makeup of the armed forces, did not seem to be over represented plus they were all lovable and relatable characters leaving the audience feeling good and satisfied at the end. Such movies in my opinion are not only thoroughly entertaining but do wonders for healthy race relations.
Again the black demographic is just under 15% of the American population and for it to approach 50% or more again and again in cast after cast on television, in entertainment, in media makes it look contrived, political, and in your face DEI that is insulting to many. I do not think it helps race relations at all.
There have been some exceptions such as Hamilton with a predominantly Black and Latino cast playing characters that were white. It played on Broadway for 6 years plus road shows wining 11 Tony Awards and a Pulitzer for Drama.