It’s only declining depending on what you’re looking for. RnB has changed because the music biz has changed.
In the past the method to get on was get signed, then came artist development (vocal coaches, choreography, etc.)then the the label did the leg work to make you well known the cutting process was different. Guys like Tiller, PnD, Tory, etc. in the 90’s early 00’s would just be relegated to being songwriters because they aren’t great singers but they have nice pens.They can croon but aren’t “sangers”. So that’s one part. I think the Dream was a big groundbreaker for guys like that
Second part about what’s different today is content. Back in the day because there were more people in the process , if a song wasn’t a “you are my world” “ I wanna make sweet love” type ballad. A lot of shit had to be innuendo or alluded to. If a cat wanted to make a record about just fucking a bunch of women while off cocaine the record was made in a somewhat classy type way because RnB had a type of image to still live up to according to the industry. Now the shit is direct to consumer little to no middleman in the creative process. So a lot of that has been essentially been removed. A lot of cats records sound like how niggas would go about it on the day to day.
Shit just different and I get it. Some people immediately turned off if an act can’t Sang Sang. I’m cool with that. Some people are turned off when an act isn’t sultry in the lyrics I get that too. RnB just in a different place now from lyrics to production. I fucks with it but people who don’t just gotta search a lil harder. Cats still making that kind of RnB that y’all looking for now too which I also listen to heavy. Things go in cycles, the type y’all looking for will become the popular RnB again.