The strange thing for me is how much time we spent in the early 2000s discussing website responsiveness and quick loading times as ways to improve user engagement and productivity. Although I can't provide any statistics that I'm intimately familiar with, I recall reading numerous case studies where improvements in responsiveness resulted in significant productivity gains for end users. If I recall correctly, this wasn't just about dial-up connections and multi-second page loads. This belief was still prevalent even when discussing sub-second responsiveness.
Perhaps the direction of the case studies started to shift, and we stopped hearing about it. However, it seems to me more like we pushed hard to reach a certain level of speed in our computer usage, then became complacent, and have been regressing ever since.