The middlings are the problem. Users tech savvy enough to think "wow, that was so fast!", but not tech savvy enough to look and see if there was a 404 or whatever, in the web console.

Which, sadly, is the tech level of most UX people.

Unskilled users are just happy it was fast. Why would it take time, it's a computer!

It's a little like psychiatrists. A surprising number have loads of issues, and go into the business to help themselves.

But this skews perception.

UX people make all sorts of unfounded rules up, many created decades ago, when almost everyone was a "new user".