Yes, high mileage works, but with over 85% of the American running population injured each year, there's something obviously wrong with the way they are running.
Yes, you get to work with elite runners and there's good evidence that runners who make it to that level had good running mechanics in the first place (American runners not being as superior as a high number of east African elite distance runners when it comes to form).
But, could you take a team of injured high school runners and get them running high mileage, uninjured with no focus on form? Most likely not. You would send them off to PT's and doctors.
By focusing of form, you can get people running high, uninterrupted mileage with no injuries. I've done it and had a group of injured kids go from 5:00-6:00 miles to 4:15 to 4:35 miles in a seven month period of time. High mileage and AT development did work, but only because they were injury free and focusing on economy of motion.
Or, you can just cherry pick and thrown a dozen eggs against a wall and rest your laurels on the runners that come back uninjured/eggs unsmashed, as do most coaches. What's the injury rate of your runners over the past several years? How much better could they have been with no injuries?
And to the BroJos who posted the quote, didn't Wejo's career end short due to injury and didn't he see a number of specialists with no true avail? I saw footage of him running and there aspects of his mechanics that were potentially injury producing.