The reason I learned to speak RP is the same reason people are taught Hochdeutsch instead of Bavarian German, celle de la bonne société parisienne instead of Québécois, namely that those versions of the language are generally accepted as, at the risk of sounding elitist, the “proper” way of speaking the language.

You really seem to be conflating accent with dialect. Continental Europeans tend to learn standard British English, which is the constructed dialect used in quality publications and in government. Standard British English doesn’t give you information about how things are pronounced. If you speak RP, that suggests that you sound like Queen Elizabeth.