This is so true. I never, ever learned Spanish from formal classes. When I started doing immersion and absorption learning, I became close to fluent in a couple of years. I now watch TV, read, listen to audiobooks, etc. in Spanish all the time and can speak and think in it with little effort. I've also started to notice I'm learning "the rules" without actually knowing anything about them. I'll just see something written by lower-proficiency SSL speakers that looks weird or off to me, and I have no idea why I know it's wrong. I just do - exactly like with my native language. I'm still not a perfect speaker, but I've never had the level of success with formal learning that I have with absorption learning.