> What if the "value" is actually less than the cost of the task (but it's still absolutely necessary)?
This is a false premise. But it's surprising how many people seem to hold it, to their peril.
> I have a feeling that all you're doing is shifting the complexity around. The underlying complexity is still there
That's right, but do you agree this approach moves it to a place where it makes more sense, where it informs good decisions and is manageable?
> it's impossible to accurately estimate a development task and impossible to measure developer productivity
It's not impossible, but it's not something we as a society or an industry have a common fine grasp on. On this topic, I like best the books by Doug Hubbard: "How to measure anything" and "The failure of risk management: what is it and how to fix it".
It just requires yet another unusual mindset: probabilistic thinking, in addition to the above-established value-based thinking. You have to use a technique called calibrated probability assessment. We started practicing this at my workplace, and it seems to be working as intended, but we're not well calibrated yet.