Anakin only destroys the Sith on an absolute technicality.

I feel like that’s the entire point. The Jedi misinterpreted the Prophecy. This is a common mythological trope.

Anyway, Chosen Ones and prophecies are dumb and Anakin isn’t the OT’s protagonist, but that’s just my two cents. You guys can believe whatever you want.

Concerning the stormtrooper thing, I think Lucas just meant the Empire in general would keep fighting, and the bad guys would be the successors to the stormtroopers. He didn’t literally mean stormtroopers. Lucas often makes silly little mistakes in SW terminology.