How is transparency worse than smoke screen that we have today? For example healthy and good websites could rank according to good content, good optimization, variety of multimedia content, decent design and UI etc. You can't have too much of good things and qualities. That would be something like writing a too good book or making a too good product.
Because the rank algorithms are subjective heuristics, not absolute metrics. All rank algorithms always have been. It started with the link metrics, then people started gaming that. It's been a signal/noise war ever since.
It's also dangerous to ask for the exact criteria because they are ever changing. Google et al don't want to be prescriptive about what a good site is, they want to recognize what a good one is. You make a good one, they'll figure out how to recognize it.
They can't sit down and publish "The Definitive Guide to a Good Website". That's just not their role and it will be out of date before it's published.