On the other hand, I only learned (my native) English grammar by studying another language. I mean, I used standard English intuitively, but couldn't have told you any of the technical terms. I agree with modern educators that explicit grammar instruction beyond a very, very basic level should not be a high priority. Exposure to and guided close reading of complex texts sharpens grammatical intuition, right alongside all of the other benefits of an advanced reading level. Knowing deep grammar does not so automatically improve textual interpretation.

This is speculation, but I wonder if the period of emphasizing explicit grammatical instruction wasn't an accidental interregnum. That is to say, back in the days when Latin and/or Greek were part of the ordinary curriculum students learned grammar much as I did, as a "natural" excelerant to interpreting a foreign tongue. Once those languages were dropped educators noticed students couldn't do grammar analysis anymore, and so tried teaching it directly, without fully considering when and why it might be useful. I don't know how well the dates line up, but it would be interesting to look into.