Hey,
As a Black dude, I can tell you that neither I nor my family (and friends) ever avoided post-1975 music. Hell, most of the stuff we jammed to came from that period. Plus, as much as people disparage disco, some serious jams came out of that genre as well (e.g., "Beyond the Clouds"-Quartz, "Work it Out"-Stargard, "Let No Man Put Asunder"-First Choice, "Reaching Out (for Your Love)-Lee Moore, "Devil's Gun"-C.J. & Company, "I'm Caught Up (in a One-Night Love Affair)-Inner Life, "At Midnight"-T-Connection, etc.).
Peace,
Big Stacks from Kakalak