“designers themselves often can’t agree what constitutes good design. You can surround the creative process with plenty of bluff and bluster but no-one can say with absolute certainty when the ‘right’ solution has been reached.”
This is a lot like scriptwriting. Ask different people to point out where one act ends and another begins and you will find disagreement. One group may draw a clear line and separate one act from the next but never agree where that line should be placed. Another group will point out that “something happens” at some point (another variable that is ill-defined) and then 5 pages later (give or take 5 pages) something else happens.
There are a lot of things one can learn about writing from others but most of it is theory and it often falls apart in practice.