I think this hits the nail on the head. Complaining that the current understanding of REST isn't exactly the same as the original usage is missing the point that now REST gives people a good idea of what to expect and how to use the exposed interface.
It's actually a very analogous complaint to how object-oriented programming isn't how it was supposed to be and that only Smalltalk got it right. People now understand what is meant when people say OOP even if it's not what the creator of the term envisioned.
Computer Science, and even the world in general, is littered with examples of this process in action. What's important is that there's a general consensus of the current meaning of a word.
Yes, the field is littered with imperfection.
One thing though - if you do take the time to learn the original "perfect" versions of these things, it helps you become a much better system designer. I'm constantly worried about API design because it has such large and hard-to-change consequences.
On the other hand, we as an industry have also succeeded quite a bit! So many of our abstractions work really well.