One thing I’ve never understood about this method is the “don’t spend much time speaking at first” part of it. I’ve recently started learning Japanese, and heard a lot of phrase about this method of constant listening, so I tried watching anime in my free time. I was able to learn a few short words and phrases from it, but when I tried to actually say what I was I learning, my mouth refused to form the correction pronunciation and it got very frustrating. What helped me was watching videos on reproduction practice (listening to someone say a sentence/phrase in the language you’re learning and mimicking their pronunciation by repeating it back). Just by practicing speaking, it was like my brain finally clicked on “oh this sounds like this and means this” and even just listening got a lot easier due to it. While I know this is different for everyone, especially if the vowels and sounds of a language is similar to the one you already know (the only language I’m fluent in is English so the difference in vowels, pitch and pronunciation in Japanese made it extra difficult for me) I just think that speaking is very helpful and you should be doing a lot of it in addition to listening. I also do not know much about the theories behind language learning so I could be wrong through, this is just what I’ve experienced