The question was very clear - do you want to leave the EU, yes/no. People voted yes, that means, leaving completely. The meaning of the word is quite plain, it isn't some vague idea, although anti-Brexit people have been coming up with all kinds of explanations for why Brexit should never happened, of which that is one of them. Spare me. It means leaving, as in, not being a member or paying the EU any money any more.
The constitutional crisis and mess that followed was created entirely by people who desperately wanted to not do what they had promised to do. Those people have now been cleared out at the last the election, or so it seems at the moment.
"if there hadn't been a referendum, either the MPs would have agreed on a specific Brexit proposal"
I really wonder where you learn about British politics. The problem was created by MPs refusing to implement the vote they gave people, and doing everything they could to then weasel out of it. The only reason they granted a referendum at all is they were sure they'd win, and because UKIP were forcing them to. There is zero chance they'd have ever agreed on a specific proposal in the absence of a referendum.
pure mob rule ... I'm not generally opposed to any sort of plebiscite
You clearly are. Calling them "plebiscite" and "mob rule" is a pretty big give away, as is this belief that simple questions with simple answers are some huge intellectual puzzle that somehow politicians are incapable of solving.
Brexit was and is the right decision. It is an excellent example of why referendums are a good thing. Staying in the EU dictatorship much longer would have destroyed British democracy completely. Look at how much of a fight the establishment put up over leaving. It's a toxic, regressive project that runs counter to the last 200 years of history, in which vast empires were all steadily got rid of, often at great cost in blood, by people who recognised the huge value of nations. Look at this thread: arguments that MPs are somehow better than the people and have a natural right to rule. No thanks.
However, regardless of our respective personal views, you contradicted yourself earlier. Brexit is now the policy of the indirect form of democracy as well as the direct form. It is, by your own logic, the right decision and by implication, was the right decision before as well.