Even allowing for modern tastes and attitudes changing, this is an awful movie. Anthony Quinn cannot save it and no one else in the movie is even halfway decent. Katherine DeMille as his wife seems to be shooting for "stoic" and landing on "comatose". As was said of an equally terrible film on MST3K, "Someone with attention deficit disorder edited this movie." Things just kind of happen for no apparent reason and scenes fade out like the director got bored (and if he did, fair enough.) Plots are sort of vaguely started, then peter out.
And of course, the only thing this has to do with the actual 1924 Kentucky Derby winner, Black Gold, is the horse has the same name and was owned by an Indian (in reality, a Cherokee named Al Hoots. He was dead before Black Gold won the Derby and that's about all he has in common with "Charley Eagle.") The movie can't even be bothered to get the Derby roses the right color (unless the film stock is SO degraded those were red at some point.) Even the softened-up version of the horse's story told in Marguerite Henry's "Black Gold" is more accurate than this disaster area. This is an excellent example of a case where just because you have some spare money and actors on contract does not mean you have to make a movie.