I was working with some researchers for a couple of months and I was fascinated how they have their own world of scientific publications. You could be a totally competent scientists or engineer and not know a lick of English.
They'd really only go to English publications as a last resort, and people I'd guess weren't under a ton of pressure to publish in English either.
Since then I've actually noticed this is a trend in larger countries. There is some kind of critical mass of people which once reached makes them completely capable of living in a linguistic bubble. Mostly this is simply a question of how variety of media you have available to consume. Once it's high enough and you have the major western stuff dubbed, you can kinda cost with your local language. Compare something like Poland (where surprisingly few people speak English) and some place like Estonia (where everyone speaks English)
Spoken fluency sucks. Reading and writing English is much better.
When I lived in Japan, and eventually achieved some basic fluency in speaking Japanese, communicating with my coworkers often consisted of English vocabulary, in sentences using Japanese pronunciation and grammar.
The reason for this is simple. They had plenty of access to English written material, and needed to read and understand it in order to do their job (computer science research).
But they had very little interaction with native English speakers on a day to day basis, so few opportunities to practice real time conversation. Which is the only way I know to actually become fluent speaking a second language.