But TD, young children at home learn a language by osmosis/exposure: by hearing the words, thousands of times as a baby and later as a toddler.
The parents are no language specialists.
The kids become fluent in a couple of years.
Why can't the same pattern work in a classroom?

As a young adult, I learned a second language by watching movies (a lot of them) in that language: My first movie, did not understand a word, not one. Second movie, a couple of words, etc. Why can't this work in a classroom?