A general rule that I try to follow is “never write something which someone else has already written better”. Rather than give a numerical scale, I’ll list a few distinct ways that pieces can satisfy this rule. I’ll give examples of each from my own writing, with the caveat that they are not necessarily very good pieces—just examples of my own reasoning regarding their novelty.
Novel theory/observation/interpretation (or at least novel as far as I know). Ex.: Computational limits of empire
Carving up known ideas differently, e.g. by pointing to a particular sub-idea or creating a handle. Ex.: The broken chain problem
Taking a well-known idea from one area, and applying it in another area. Ex.: Competitive markets as distributed backprop
Analyzing something which has been analyzed many times before, but usually incorrectly, so it’s hard to sift signal from noise. In this case, the novelty/value is in making the analysis visibly correct. Ex.: Accounting for college costs
Translating some piece of metic knowledge into a more transmissible model/technique. Ex.: How to find unknown unknowns
Accessible explanations of technical ideas. Ex.: Queuing theory without math
Arguing that some known idea/problem is more important than people seem to have noticed. Ex.: Coordination economy
Note that these are ways that a piece of writing can be novel, not guarantees that nobody has ever written the same thing before.
Side note: if using a numerical scale, I worry about confusing novelty with importance—the example scale in the OP seems to mix the two. Perhaps a better approach would be to give handles for several different ways things can be novel, and then use those as tags?
Hypothesis: they weren’t any more innovative than anyone else; their language and culture just got transmitted over a much larger area. In the wake of Alexander’s conquests, Greek became the working language of government bureaucrats across most of the Middle East. It quickly turned into a status symbol and a credential, sort of like a college degree today. Speaking, reading and writing Greek automatically put you into the educated social class. A working knowledge of Greek culture followed along naturally with the language.
Without Alexander’s conquests, I very much doubt that Aristotle’s name would be at all known today.