She doesnt suck on clay. She has won a French Open, been to atleast the quarters of the French most years since, won many Premier titles on clay, beaten everyone on the surface. So if one says Serena sucks on clay then you must say Kuznetsova, Sharapova, Ivanovic, Capriati, all suck on clay too, as she has achieved as much or more than all of them. The only clearly better or more successful clay courter in the last 15 years is Henin.
Serenas movement is not a weakness. She is one of the best movers of the current field in fact, even older and past her movement prime. Name a current list of players who move better, and you will be lucky to find a handful.