[monoideism]

> he first phase of language learning is mostly theory. Mostly vocabulary and grammar. The second phase is mostly reading, reinforcing the theory, forming a good understanding of how the language is used. Additionally writing things, chatting and the like. Third phase is immersion with speaking and listening.

This is an excellent description of the process I used to learn to speak 3 foreign languages to a level of professional fluency, and 3 others to conversational fluency (this was in my 20s, I now only maintain fluency in 2 languages, although sure I could regain it fairly quickly).

I do think this depends on the individual. Some people successfully use other techniques.

[bayesian_horse]

I don't think it depends on the individual, but rather on goals.

If you want to speak a language in a useful but relatively broken way, as fast as possible (for example as a refugee), you might want to prioritize a smaller amount of theory and more practice early on. But that would actually prolong the time to proficiency.