Word definitions are determined by usage, sure. Guess what, though? Usage is defined by what people think is correct, including how they argue about that usag

Word definitions are determined by usage, sure. Guess what, though? Usage is defined by what people think is correct, including how they argue about that usage and what it "should" be. If you embrace descriptivism, you don't get to reject prescriptive arguments as "wrong" on the basis that ZOMG, there are no rules. It's like saying a policy arguments is "wrong" because a poll reveals that people exist who don't agree with that argument - you're not even talking in the right context. Or, put another way, if enough people continue to spell "past" as "passed" ("I went passed the sign..."), then eventually one of the definitions of "passed" will include "alternate spelling of 'past'". But someone isn't wrong to say, "That should be 'past', not 'passed'.", even if some people are spelling it wrong.