I flew with Qatar not long after they started advertising their five star status. It was a journey that started in the UK and transited through Doha. The plane to Doha was packed with people, including lots of families with outrageous amounts of hand luggage to accompany the many children. This was one of the most crowded, noisiest, messiest and generally unpleasant long haul journeys I have made - the flight crew had no control at all and made themselves scarce. Doha airport was utterly uninspiring, although not objectionable in any way (most large airports are anything other than "fun" unless it is your first flight ever).
On the return they changed the timing of the first leg (back to Doha), scheduling it for departure some two to three hours earlier than when I originally booked it months earlier. I contacted the airline about a week before departure to reconfirm my booking - they reconfirmed (by fax, I still have it as a prime specimen of failure) but never mentioned the changed time. By the time I went to check in on the day, all their staff had left and I had to at my own expense buy a replacement ticket with another airline. When I took up the matter with Qatar Airways (UK base) there was only the very feintest of apologies with a strong attempt to wriggle out of refunding me the full cost of the extra ticket. At this time they had a five star rating for first and business, not economy.
Public approval of airlines has long shown trends somewhat akin to those of the opinions/interest in celebrities rather than cold, rational evaluation. As a result, by selective publicity and the right sort of stroking of the right parts, a lot can be achieved, including boosting myths and ratings. No airline is reliably good but some are better than others - although unassuming airlines can quietly come up with remarkably good service that the famous ones conspicuously fail to deliver, at least some of the time. The proof is in the eating as they say, and just because you had one sort of experience once does not mean it will always be the same with that airline. However, for conspicuous flouting of the EU law on denied boarding (they said I was too late while letting others on while I was standing there - a case of "the computer says"), after travelling long haul a lot on KLM I totally stopped flying with them and never will again. Some things abruptly decide matters completely.