What is the ranking supposed to reflect, exactly? Quality of education? If the programs have the same instructors, same facilities, same curricula, etc., why wo

What is the ranking supposed to reflect, exactly? Quality of education? If the programs have the same instructors, same facilities, same curricula, etc., why would we expect a small change to admission criteria to affect rankings of the program? I feel like this kind of change most likely reveals that rankings likely have little to do with quality of instruction; just another case of selectiveness being used (by employers, by graduate schools, whomever) being used as the proxy for "quality" of candidates and the whole process of education is of secondary importance if it's considered at all.