True. But doing a class with no practice outside class is also pretty limited.
Living in China is the best way to learn the language, but only if you put in the effort too. I knew plenty of westerners who lived in China but put no effort in to learn the language. You have to do both immersion and study by yourself.
During Covid I learned a good amount of Chinese sitting home alone.
When I had the chance to sign up for an evening class, the rate of learning exploded.
When I finally had the chance to visit China, there was no comparison to the immersion.
"Learning things by yourself" is amazing when that is all you have.
It means you're never completely limited.
But it isn't a substitution for an immersive learning environment.