You're just saying "Everyone should use Chrome, otherwise the web would be balkanized". Or, taking it to the extreme, "every book in the world should be written in English".

>I should be able to read code written anywhere in the world and understand what it does

You are, but no one promised "without any effort". Almost every developer of not English-speaking origin put that effort, why shouldn't you?

>You wouldn't be able to contribute to an open source project unless it happened to be written in a language that you knew

You've just described the status quo.