I'm not so sure about the "samey" thing and can't see how it all sounds the same anymore than music from any other era or genre! I know lots of people who don't like Scottish fiddle music because they say it all sounds the same. You could say the same though for many, probably most, genres.

So yes some R&B and Rap etc does sound much the same as the rest in the genre but not all modern music is of those genres and anyway much rock'n'roll, blues, fiddle music, bluegrass, chamber music etc sounds pretty much the same as other rock'n'roll, blues, fiddle music, bluegrass, chamber music etc.