I took three years of Spanish and got an A every semester. Even when it was still fresh in my mind, I was nowhere near able to hold even a very simple conversation. And now just a few years later it’s all totally gone from my brain.
My mother’s native language is Spanish and she never taught me, which I resent her for. But I still find it incredible how shitty my public school education in Spanish was. We really should be teaching kids a second language from kindergarten up.
Of course non-immersive learning works, it’s silly to say it doesn’t. “Comprehensible input” is a pseudoscientific term for a theory of learning language; The teaching method maybe works better for some people, but the theory largely lacks evidence and at its core is impossible to prove.
Learn that way if you want to, but don’t assert it’s the only way to learn a language “that works”, it obviously isn’t. I know multiple fluent bi and trilingual speakers who simply did 90% of their learning at school.