You're absolutely correct that URIs are well-regulated, well-defined, and easy to understand for those with appropriately technical backgrounds. You're also correct that users don't need to understand in significant technical depth how URIs work in order to use them for most daily operations.
In my opinion, what's changed is that someone won the political battle between "URIs are so simple and well-defined! Everyone understands them." and "Users don't understand URIs" camps.
With that said, it's perhaps worth considering that most users might regard computers as essentially magical and fundamentally incomprehensible things. In such a context, could it be possible that it might actually be too much to ask for your average user to have a good operational understanding of something that seems to them to be fundamentally incomprehensible? A great many people have already learned helplessness in the face of technology. Could it be that decades of exposing people to the elegant simplicity of URLs has not created widespread operational comprehension?
(What's the alternative? Just stumble into the pits the dogma didn't provide for? If I'm hurt, it's the will of the Web? – "Nexus vult", as the web-fathers put it?)
In my opinion, what's changed is that someone won the political battle between "URIs are so simple and well-defined! Everyone understands them." and "Users don't understand URIs" camps.
With that said, it's perhaps worth considering that most users might regard computers as essentially magical and fundamentally incomprehensible things. In such a context, could it be possible that it might actually be too much to ask for your average user to have a good operational understanding of something that seems to them to be fundamentally incomprehensible? A great many people have already learned helplessness in the face of technology. Could it be that decades of exposing people to the elegant simplicity of URLs has not created widespread operational comprehension?