I already addressed this when I praised her in that same post: "Her fans alone are enough to fill stadiums and thrive"
Rihanna is the complete opposite. Her pool to draw concertgoers from is much larger, but her shows are so bad that they never come back. So she has to rely on people who haven't seen her yet, which can be tough when there are no hits to galvanize them.
She's a very skillfully. She's sultry. She's goofy. She's sounds slightly absurd. She's fully engaged. She's expressive in ways that "technically superior" vocalists just aren't. She is brilliant. You have no idea how brilliant she is.