Immersion works, and it's not the mechanism people think. Plenty of people live in English-speaking countries for fifteen years and remain intermediate, while others reach fluency without leaving home. What separates them is not location.
What immersion actually provides
Not exposure. Demand.
Living abroad works when it forces you to produce language constantly — to handle a landlord, argue with a phone company, make friends, be funny, be taken seriously. You improve because the consequences of not improving are immediate.
It stops working the moment you can avoid that. People who move abroad and work in their own language, live with compatriots and handle the rest in English's simplest register plateau quickly, surrounded by English the whole time.
Which is useful news: the active ingredient is production under pressure, and that can be arranged anywhere.
What to replicate
Regular unscripted conversation. The core of it. An hour or two a week of real conversation with someone who pushes you does most of what immersion does, because it creates the same demand.
Something that forces output. A weekly call with a friend, a language exchange, a hobby group in English, a work situation you volunteer for. Anything where English is the medium and something real is at stake.
Consumption you'd choose anyway. Follow your actual interests in English — a sport, a craft, a field you work in. Not study material; the content you'd consume regardless. It builds the vocabulary you'll actually use and it doesn't require motivation.
One area of genuine depth. People who reach high fluency usually have a domain where their English is excellent — their work, a hobby, something they read extensively about. That depth then generalises.
What doesn't replicate it
Passive exposure. Background radio, films with subtitles in your language, scrolling in English. These are not harmful and they are not the mechanism.
Nor is being in a classroom indefinitely. Lessons are a tool for correction and for forcing output; they aren't a substitute for using the language elsewhere.
The advantage of staying put
One genuine one: you can choose the difficulty.
Abroad, everything is hard at once and much of it is tedious — bureaucracy, forms, logistics. At home you can aim your practice at what you actually need and skip the rest.
How long it takes
Longer than full immersion, honestly. Immersion compresses enormous amounts of practice into months.
But the gap is smaller than most people think, and it's measured against a version of immersion that few people actually experience — the one where you really are speaking English all day, which is not what happens to most people who move.
What to stop waiting for
The main cost of the move-abroad belief is that it postpones the work. People treat fluency as something that will happen when circumstances change.
The circumstances that matter are two or three hours a week of real production and the willingness to be clumsy. Both are available where you are.