There's been a shift in focus in what attracts consumers. Artists that emerge these days are more based on image/branding and "relatable" lyricism backed by cutting edge production.
During the late 80s-late 90s era there was a heavy emphasis on vocal showmanship, which is the main base of any true black RnB group.. groups like BIIM, Destiny's Child, New Edition, SWV, Dru Hill had a distinct vocal artistry (vocal layering, call and response, stylistic melisma 'runs', melody elaboration etc..) that was greatly admired during that time, which is why most of the successful artists during that time were also vocal monsters (Whit, Mariah, Brian Mcknight, Wanya, etc). Today those types of artists/singers aren't as appreciated anymore (I have a personal theory about that, but I'll make a thread one day).
Black consumers today don't particularly care out talented a singer/stylist you are because believe it or not, most ppl don't know how to distinguish that shyt.. They'd rather rappers these days sing their own hooks instead of ft a talented vocalist because the "realness" connects with their audience.
The novelty of extraordinary vocal talented has taken a backseat in our music culture.. as a result, black vocal rnb groups currently don't have an audience.
As far as Beyonce goes.. I believe she's even peeped game after releasing 4 which was a genuinely good throwback etude to traditional RnB ..with cuts like 1+1, Dance With You, Rather Die Young, Start over etc that flopped in the current market, forcing her to switch gears and really branch out artistically (in her vocal delivery, muscianship, writing) to reconnect to the audience with Self-titled. That was a huge eye opener as to how receptive the GP was to RnB music in today's market.. which isn't much at all.