Agreed, she got better and better as the series went on. Oddly enough, by the time she was closest to his level (in Carefree and The Castles), the magic between them faded away. Maybe the disparity in their dancing abilties was part of their sexual tension and chemistry.
Ginger started the 30's as the fun time Ado Annie in 42ND STREET. And continued that fun personality in FLYING DOWN TO RIO. So that Astaire thought her screen persona was too tacky to play the upper class lady in GAY DIVORCEE. But he was overruled by the public. Their sexual tension is drawn from
The contrast of her modesty and propriety and his enthusiastic let's pull out all the stops. But I also think when you represent an era, you can't continue on top as styles and life changed in the 40's. Thanks for your honest assessment of Astaire and Rogers. It needed to be said for a longtime.