You make good points as ever Jock, but for me personally the quality of this music dropped off a cliff face for any number of reasons towards the end of the seventies.
Budgets, demographics and a simple evolution of how and why African-American people made music meant that mainstream R&B fundamentally changed at that point. Of course there are exceptions since then, but really, where are the "What's Going On", "Curtis", "Friction" or "Black Bach" of the 80s and 90s?
The major artistic statements filled with craft, passion, insight and creative flair?
Where indeed are the releases which exhibit even competent skill in songwriting or production or arrangement?
Where are the truly exceptional new vocalists to rival a Sam Cooke, Johnnie Taylor, an OV Wright, Jerry Butler, or a Linda Jones, Judy Clay or Bettye Swann?
Where are the great standard songs like "A Change Is Gonna Come" or "Dark End Of The Street" or "Let's Stay Together" or "Let's Straighten It Out"?
Sutty can accuse me of ignoring a whole swathe of music, but he would be wrong to do so. I bought new US releases religiously until the mid 90s, until I woke up and was finally able to smell the coffee: that very little of it had any artistic merit, and that even average or poor discs from soul's Golden Age were functionally superior in practically every single way to even the best of the output of the 80s and 90s.