You're still stuck in your narrow view of politeness. The concept of politeness is not a constant, but a variable that changes throughout various cultures.
"Politeness" is not an objectively-quantifiable one-dimensional characteristic of a culture, sure. There are smaller traits that are quantifiable, though.
"Care taken around inattentive strangers", for example: the difference between assuming it's someone else's fault if they stand in the road, and assuming it's your responsibility to not hit someone standing in the road.
Or "empathy for people who don't know your customs", for another: the difference between expecting foreigners to already know how to be polite in your locale, being willing to teach foreigners local etiquette, and feeling a responsibility to learn multiple foreign cultures in order to react to each foreigner with the etiquette of their own culture, which is a truly strange feeling I've only experienced while in Japan.