Language classes in school are horrible. You’re going for an hour a day for 180 days, with significant gaps every few months, and moving at the rate of the slowest learners in the class.

500 hours of constant, immersive study would likely get you most of the way there, which is not the same as being immersed for 500 hours without study :)

I thought I was doing well with Duolingo once, then realized, 40 hours in, that I had almost no concept of formal/informal, and barely had any verb conjugation or grammar.