Much of the criticism of Ryanair here and elsewhere comes from prospective customers thinking that their flight is going to cost a lot less than it actually does, once baggage/check in/credit card etc. charges are added. They feel tricked. I think some of this criticism is unreasonable (takes cover at this point!) because, in my view, the expection of such low fares is unreasonable.
Yes, Ryanair's "base" fares (e.g., for travel within the next day or two) can be high but, for the routes I'm familiar with at least, generally this is not the case. I think some historical perspective is called for. I have been flying regularly between the UK and the Spanish Mediterranean for twenty years and, fortunately, still have a record of what the earlier flights cost. In the late '80s I flew mainly on a "seat only" basis using companies like Jetsave and Thomson. A typical July/August return fare was £150. Now remember, that was twenty years ago. When I consider wages/salaries at that time and inflation since (not to mention the cost of jet fuel) the real cost was much more than the same journey today with Ryanair (if booked at the same point in advance). Remember, too, that these seats on charter flights were themselves much cheaper than those on airlines like Iberia.
Perhaps some of the criticism of Ryanair comes from passengers who do not have this historical perspective and do not, therefore, realise how low the cost of air travel now is in comparison with the past.