If you knew AI to be radically more transformative than other technologies, I agree that predictions based straightforwardly on history would be inaccurate. If you are unsure how transformative AI will be though, it seems to me to be helpful to look at how often other technologies have made a big difference, and how much of a difference they have made. I suspect many technologies would seem transformative ahead of time - e.g. writing, but seem to have made little difference to economic growth.