Priceonomics seem to have created their rankings based solely on people's comments on the Skytrax website - they even state explicitly that the set of people commenting is not representative of airport users. You can always try to form conclusions from a dataset, but in this case rankings are not based on the average flyer - they are likely to be weighted heavily towards people who've had a bad day and want to let off steam. I'm dubious this is a good starting point for any kind of statistical analysis