I agree with a lot of the comments here, especially this:
Even worse is the new trend of web pages optimizing for page load time. You wind up with a page that loads “instantly” but has almost none of the data you need displayed. Instead there are 2 or 3 AJAX requests to load the data & populate the DOM. Each one results in a repaint, wasting CPU and causing the page content to move around.
Loading spinners are an anti-pattern. We shouldn’t use them unless we absolutely have to.