The Golden Rule of Language Learning

The Golden Rule of Language Learning: Absolutely any method of language learning, as long as it includes regular exposure to the target language, will eventually yield fluency if followed faithfully enough.

The Rule can be proved by a thought experiment. First, think of a target language (like Chinese, or Arabic, just to make things hard). Next, think of whatever language-learning method you want, as long as it includes regular exposure to the language. You can make it as ridiculous as you want. For example, it might include drilling gibberish that has nothing to do with the target language. Or even drilling blatantly false lies about the target language. Make it as ridiculous as you want, but it has to include regular exposure to Arabic or Chinese or whatever target language you chose.
Now imagine your messed up, horrible method of language learning is imposed on a newborn child in the target country. By the time they are 18 years old, they will be fluent in the target language. They might have been driven clinically insane by your sinister language program, but they will know their language, and know it fluently.
NOTHING BUT EXPOSURE IS NEEDED
There are examples of children who were unable to speak a word due to disabilities, like paralysis. When technology provided them a means of communicating, such as a keyboard they can type into, they were immediately able to communicate clearly and fluently in the language with that technology. No “hands on practice” necessary.
Everything but exposure is extra. The trick to efficient language learning is designing all these extras so that they speed up the process. But however inefficient they may be, exposure alone will eventually yield fluency.
WELL, MAYBE ONE OTHER THING IS NEEDED… ATTITUDE
I guess I should add this disclaimer, that a good attitude is also necessary. I admit that if someone is actively trying not to learn a language, they can succeed in not learning it, even with regular exposure. But if that’s the case, that person probably wouldn’t be reading my articles or browsing forums about language learning.
BUT… BUT… BABIES ARE SPECIAL AND MAGICAL
People may argue that babies are a special case, that they have an innate advantage learning languages. Whether or not that’s true doesn’t really invalidate the thought experiment. Grown men and women sent to a new culture eventually learn the language if they try to (ie, if they have a good attitude about it). Accent is another thing, I’m not sure how accent relates to whether or not a person is fluent. On the other hand, a little accent isn’t necessarily a bad thing. A French immigrant to the United States, for example, can use his/her accent as a tool to help attract a lover.
CONCLUSION
What’s the point of the Rule? It lets us stop pouring energy into fighting over the right language program, and pour that energy into the language instead. For someone who just wants to learn one extra language, it’s probably better to just find a “good enough” method and pour energy there. To find the “best” method (it probably varies from person to person), would take more time and energy than actually learning the language.
Some methods of language learning may be better or worse than others, but there is no “wrong” method, as long as there’s regular exposure to the language. It’s like the saying goes, “most of success is just showing up”.