What's the difference between "you" and "one" in the indefinite?

It's generally regarded that the two are grammatically acceptable pronouns in American English. However, "one" is also considered to be more formal than you and excessive use of the word can lead one to appear as overly haughty or pretentious. One can use the pronoun "one" as an impersonal pronoun that's representative of the average person - this generalization can lead to a sense of social superiority.

One of them isn't really more correct than the other - however, "one" can sound rather pedantic when used in relaxed or informal settings. This is realized in the object case when "one" sounds quite odd - "When lemons are handed to one, one should make lemonade."

Sources: Grammar Girl and Capital Community College Foundation

Unless I'm mistaken, One/oneself is talking about a collection of people, IE: "One cannot simply walk in to mordor" means no one can. Whereas You is personal, IE; "You cannot simply walk in to mordor" means that you alone can't walk in