As an amateur marathoner I hit my best PR 10 years ago, the year I quit stretching. I don’t credit my time to not stretching, I credit it to years of training. But I had read enough about how stretching simply doesn’t help to give it up and concentrate on running.
I continue to do yoga two or three times a week, just because it felt good and I like it. But I stopped stretching completely before and after runs and I didn’t notice any difference at all.