I would agree that it's a measurement problem in the sense that we don't even know what or how to measure it. But your analysis is silent on what an error is so I'm not really sure what you think you have gained by it.
> It's not clear to me how you can say that a new heuristic is "far inferior", nor how you can say that the academics lack a good framework but you presumably don't. How do you know what a good framework would look like?
It isn´t that I have something that they don´t have. It´s far more sinister than that. And here is my argument:
The best tool we have at the moment is: you play it (any given set of ideas) out in the real world and look at the consequences in terms of elevating/reducing the amount of suffering that is at the basis of the human condition - after all, that is the end goal of political heuristics. Popper´s and Rawl´s ideas are not "new" in the sense that they have been extensively tried in the past. They were murderous beyond belief but somehow that is always forgotten and never accounted for as linguistics is used to disguise the actual end-result of the experiment by saying that "they have not been tested at all" or that "these are new cutting edge ideas".
As an example, we can take a look at communism. The total body count that was produced under communistic regimes would probably make for a giant mountain that would take months to climb. Yet somehow you always hear the slogan "that wasn´t real communism" as a rebuttal to the inherit evil of said set of ideas. If you pay close attention, parse the ideas given and see if they have previously tried or not, you can most often tell that the vast majorities of proposed changes are new reformulations of old and debunked shit.
Example: Marxism views the world as a battle between two groups, the rich and the poor. 3rd wave feminism views the world as a battle group between men and women. This is an over-simplification obviously but what I am hoping to demonstrate here is that it is the same old wolf in sheep´s clothing. We don´t need to replay that experiment to know where it will end up. This is the best we can do at the moment. Am I happy with this methodology of evaluating ideas? hell no. But we have no mechanism that performs any better. And as for the academic class, heck, it is they that purposefully spread these reformulations to the younger generations by actively reworking old debunked ideas as their own "new" takes on how the world ought to be - which is why I tend to believe that academia (especially the social "sciences") is far more sinister than first meets the eye.
Note: I used marxism/communism here as an example just for convenience. I could have just as easily used the Veil of Ignorance or the argument of intolerance to demonstrate that same principle. They have been tried many times before and they were incredibly counter-productive. In spite of what most people think, the modern form of western societies can be seen as a function of the set of most effective ideas that have been tested to date (effective = generate the most amount of reduction in overall human suffering). It isn´t perfect (it´s a heuristic after all) but in comparison to all other tried and tested set of ideas, it is the best we can do atm. Besides, even in the west, small variations of these ideas are currently being tried within each nation state. It is a process that takes time but as these experiments unfold, we will learn something new and converge on a better solution once one is found.
To go way back up to your original post I kind of agree with you on subjectivity but I really don't see how you're then arguing that your framework demonstrates that Rawls etc have been 'debunked'.