I do the same and have the exact same thoughts about corners dead ends etc. I also cant seem to find the "consistent mental model" seems very scattered.

what site is a great example of good UX?

One of my go-to examples is http://www.gov.uk. Obviously a very different site to Facebook, but the way it combines the content from hundreds of individual sites while still making it easy to navigate is impressive.

To be fair, Facebook's UX is always going to be a bit of a nightmare just due to the sheer volume of disparate features stuffed in - the 'iTunes effect' as I've just called it - so the move to focused apps for specific features is probably a good thing.

To be not so fair, I get the suspicion that the UX is left deliberately confusing in places, especially the constant rearranging of privacy settings, to get people to share more than they would otherwise.

I know it's text based but still, the gov.uk is blazing fast. Looked under the hood, seems like they're using client-side template rendering via Mustache, and JQuery.

Not sure what the back end is written in, saw a reference to Flask in a javascript comment, so maybe Python.