I think beyond that, the anger is that female r&b is no longer controlled like it once was. Diddy, Irv, Dupri, Timbo/Missy, etc all had their artist (or artists) who they were caking off of. Now the game has completely changed, no one cares if you were a "super producer" anymore and the biggest r&b women are largely signed to labels that aren't using a 90s/00s playbook. SZA doesn't have a Diddy telling her exactly what to do or demanding she make a particular style of song (say...a ballad) just because that was hot 15 years ago.
I can sympathize with Diddy on some things...like I'd imagine he's watching SZA's career being fukked up and wondering why these dudes can't manage a woman act properly. But this is the same guy who won't admit he's completely out of touch with the music world now, cannot get an artist to pop to save his life, and is bitter that all these popping artists aren't his to control.