The main issue with the the usual approach of language learning is the focus on grammar, like if doing useless grammar exercises would improve your grasp of grammar and sentence construction rules. It doesn't help much actually.

I've learned more grammar watching tv series than actually studying grammar for years in school, and my pronunciation improved too. Now many things just come naturally.

And i can understand the issues he's having with pronunciation, without a constant reference to how something should be pronounced you tend to ignore the correct pronunciation of words you don't know (but you can deduce the meaning while reading) an build up a collection of words with completely broken pronunciation that you will end up using in actual conversation. With hideous results...