No, there's not “a few exceptions”. It's really rather common for aites not to display in Reader Mode at all; far too common to be called “exceptions”, and nowhere near “a few”.
Not particlularly angry (at you, not at all; at web sites, a little), just a very different experience than yours: Many articles I come across refuse to display in reader view.
What's "forced reader view"? If I could force it (and get a readable result every time), there'd be no reason to be even a little angry.
Press CMD+Shit+R to force reader view, it usually works if it's an article. On iPhone I think you can force reader view by long pressing the reader button on the side of the URL bar.