I can tell you location has a *huge* effect on the rankings.
Some examples:
Swap out the 18 holes at Morfontaine for the 18 holes at St. George's Hill. Is the Morfontaine course going to stand out in Surrey? Is not St. George's Hill going to blow away everything in Europe?
Or, take my two best recent courses, Tara Iti and St. Patrick's. Tara Iti was quickly rated #1 in New Zealand, whereas no matter how good St. Patrick's is, it won't be ranked ahead of Portrush or County Down or Ballybunion for a decade or more. Now, if you swapped them and put St. Patrick's in NZ and Tara Iti in Ireland, do you think they'd be ranked the same?
There are so so many of these effects throughout the rankings that it makes them impossible. And that's why I much prefer just calling the course a 7 or an 8 and leaving it at that. Even in the Doak Scale there are small adjustments for location . . . sometimes I might rate the best of the 5's in one spot a 6, to state a preference, even though it might not hold up with all the 6's in Philadelphia. Bias is inevitable.