I'm glad someone brought up BJJ. I'm ~4 years in, and it works exactly this way. The day to day doesn't seem like you're learning that much. In fact, I don't even feel like I know that much after 4 years. But, when I roll with high belts now many have to really work to get me. And like you said, if I go against someone who has never grappled before, I can gently fold them up without breathing hard.