I think what we tend to forget it that neither artists ever had a dancing background. Perhaps Rihanna gets more recognition simply for being in the industry for almost twenty years, and slowly building up her empire. Even if you look at her music videos, she's not really dancing, but she makes it up through her visuals.
I don't quite understand why people think that Dua Lipa is not that good. Correct me if I'm wrong, but I don't think Dua Lipa ever had any intentions of dancing; it's just that she makes excellent Dance Music. Suddenly, this artist is thrown in to something they have to learn along the way, while we all go and critique their efforts.
Both artists have been making music for a while, and I believe that was their goal from the beginning. To compare Rihanna and Dua Lipa to Britney Spears and Beyoncé, well there's a huge difference: B&B have dancing backgrounds, which gives them strong stage presence. Yes, you can say that Rihanna and Dua Lipa have had time to practice, but they still both have a long way to get onto the level of Britney Spears and Beyoncé.
Final note: while I did find parts of the Superbowl performance to be, lackluster, I will admit that I overall enjoyed seeing Rihanna on the stage and sing all of her hits (even if that means we'll probably never have song sung from her first two albums).