There are oodles of terrible managers. There are oodles of terrible everything and we definitely remember the bad experiences more than the good experiences. Especially since a lot of what a good manager does (deflect distractions, ensure consistent prioritization, hire people who don't suck) makes it seem like nothing is actually happening.

A very large number of people really are saying that these roles aren't necessary. Larry Page famously fired all of the managers at Google at one point in the past. I regularly see people say that zero management at all would be preferable, both for startups and megacorps. Heck, the article itself is about this very idea.