I don't disagree with this, but you need a "critical mass" of textbook knowledge to get started

I disagree with your disagreement.

I started off by memorising the hiragana table, then went hardcore. Got a simple manga (Hikaru no go) and a Japanese to English dictionary and just winged it.

Initially it took me a month to read an entire volume. It gets easier.

That was 20 years ago without any of the fancy tools people have today.