We are been ordered by Allah (SWT) in Quran to obey the Prophet (SAWA) and by the Prophet to pray as the Prophet did. This means any Wudhu or worship away from what the Prophet did is invalid. The Prophet never washed his feet in Wudhu but he was always wiping over his feet. Washing the feet in Wudhu was created by some persons long time after the Prophet (SAWA).
Wassalam.