To settle this point and answer the question, I would like to invite teachers who support grammar teaching to design a lesson or series of lessons to teach pronouns of gender in such a way that a student could "learn" it in one week or even one month in such a way that a student will use it correctly more or less consistently.
Then I suggest that teachers who do not support grammar teaching, with an open mind, try this lesson or these series of lessons with their students and see what the results are.
I have no special interests in showing that teaching grammar does not work. I receive no royalties or benefits one way or the other. My special interest in all of this is language acquisition. I want my students to have the fastest results possible. If teaching grammar brings the fastest results then I am all for it.