[BlargMcLarg]

This is the same reason a lot of alternative JP learning resources recommend against traditional resources (sometimes even native textbooks, tangibly related) and favor sheer immersion instead. It's the same way many non-English speakers learned English as kids before their schools even start teaching them English. Formal education can still fill in the gaps where necessary or cover areas not usually covered in daily life, but it tends to work better as a supplement rather than the bulk of learning.

I too am against it in general, and given the sheer volume of vocabulary and little quirks required to understand Japanese, you'd probably do yourself a massive disservice waiting to dive in any longer than necessary.