I agree with everything you say, however as someone who lives in a smaller secondary city, Ryanair is often the only airline offering direct flights to many destinations. So unfortunately in many cases the choice is a €50 90 minute direct flight with Ryanair or a €250 3-5 hour trip with 1 or 2 changes.
I also like their honesty. You get what you pay for.
Lufthansa on the other hand removed everything (free checked luggage, free drinks, free food) and said that passengers would be much happier to personalise their flight experience by buying everything separately.
They're cheap and they go to some destinations where there are no other flights.
Plenty of people disagree with you and I'm one of them. If the upside is paying 10 euros for covering 1500 km I can handle the cattle-like experience for 2 hours.
My work used to take me to smaller cities in Eastern Europe. Ryanair was often the only direct flight.
I don't think the planes are dirty. The lack of seat pocket and the plasticy seats must make it easier to clean.
Luckily, a number of regional players have started to adopt to this in recent years by replacing fleets with smaller planes to offer more flexibility.
I mean there is also the whole 'order of magnitude cheaper than some competitors' thing they have going on. For a lot of people, it's worth being in a filthy plane treated like cattle for only an hour if it means they get to save £200.
There is certainly a reason why Ryanair carries more passengers every year than any other airline on earth.
It's only fitting they're gonna be buying these planes.