Rankings are just meaningless. And this isn't the evidence for it! Actually in the past they've more or less admitted that they play around with the weighting and discard if the outcome is unexpected, meaning that even by its own standards it's circular. But the fact is that rankings are one dimensional and universities are very obviously multidimensional. You can't get anything meaningful out of such compression. The researchers and students at oxbridge are higher quality, that's more or less undisputed. Other than that though, it's so subjective and personal.