I've come to think that international rankings like QS are more of a hindrance than a help, particularly for those considering undergraduate study.
My biggest issue with them is that they try to judge thousands of unis with varying specialities and sizes, not to mention extremely different cultural environments, with exactly the same criteria.
They're also skewed way too much by how well known an institution is, and this skews the tables towards bigger unis in large cities. For example, Manchester spanks St Andrews' bottom red raw in this ranking, but anyone who knows anything about UK unis can tell you that St Andrews is pretty damn good in its own right and has many of its own strengths and distinctive qualities.
People here tend to look down on the use of student satisfaction ratings in national rankings, but at least it's concrete data about teaching from people who have first-hand experience of the institution and its teaching. The QS ranking doesn't measure teaching quality at all and instead puts a massive emphasis on "academic reputation" (40%). It seems this is based on a survey of academics around the world. That means that someone who chooses to study history at Manchester instead of St Andrews based on this ranking is basing their decision on the opinions of people who know next to nothing about the places aside from a couple of research papers they might have read.
These days I really struggle to see the point to international rankings other than as a marketing tool for unis and a source of revenue for the firms that produce them.