I think it was in graduate school when the professor told us hopeful future second language teachers to always balance the practical side of language pedagogy (what works) with the theoretical side.
I love theory…I always have. It’s unashamedly fun to find the “rules behind it all” and discover the underlying reasons for why something works the way it does. In principle theory should always line up with the practical; in other words, what linguists and researchers drum up in universities as correct “language theory” should, for the average person like you and I, lead to successfully learning a language. Things like Krashen’s i + 1 or Chomsky’s Universal Grammar should help the average person understand the path that needs to be taken so that time isn’t wasted using a meaningless language learning method that will never lead to the comprehension needed to actually live comfortably in a language (like memorizing verb conjugations).
I took three years of Spanish in high school, knew a plentiful amount of vocab, passed all sorts of exams, and could (in English of course) articulate the meaning of more difficult grammatical phrases in Espanola, but the first time my Dad asked me to talk some Hispanics that he was doing business with in Spanish, I froze up and couldn’t do it. It was painstakingly hard to consciously remember the rules of the language and enter into a conversation. I also couldn’t understand what they were saying when they talked ( = no comprehension).
Language isn’t meant to be studied until your knowledge of the language grows detailed enough, it’s meant to be absorbed until it can be felt. Absorb language 「言語を吸収する」.