This is a great question! Especially with the advent of better AI translation, I think there's a very good argument to be made for asking people to write in whatever language expresses their thoughts most clearly, rather than enforce English as a heavy default.

However, if someone is genuinely committed to having the highest-impact life path possible, "learn to speak and write English fairly well" is definitely one of the useful impact skills to develop that sticks with you once you have it, and so people who are "committed EAs" learning it should be encouraged wherever possible. (Others include "learn to cook healthy & tasty food", "learn social/relational connection skills and mentalisation", and "learn to primarily value things for their usefulness not their status").