Surprising they don't mention what I imagine has to be the obvious culprit: video ads.

It's not even about advertising for me -- static ads don't bother me that much. But whenever there's autoplaying video in the corner of a page, I hate it so much. Whether it's an ad, or a news site that inexplicably thinks I want to multitask and watch their news channel at the same time I read their article. It's genuinely hard to read the article when there's constant motion an inch or two away at all times!