Michael O'Leary being incredibly rude is a key part of Ryanair's branding. If you're paying £19 for a two hour flight, you'll always have the sneaking suspicion that the airline is skimping on maintenance. O'Leary makes it absolutely clear that they save money by treating their passengers like cattle. He carefully cultivates the image of a man who utterly despises his own customers, but is far too miserly to allow an…
Ironically, I was extremely happy with everything after baggage drop-off. The flight itself was no worse than any other airline, in my eyes (I don't consider ads to meaningfully worsen a flight). The airport (Hahn, serving almost only Ryanair back then) was amazing, with super-friendly airport (not airline!) staff and short walking distances.
But their atrocious web site (AFAIK checking in required you to concatenate two random values and enter them in one form field, in the one working flow out of the 3-4 that were offered) and their outright, aggressive rudeness left a much stronger permanent impression than the (probably low) price, the two-hour bus ride to the middle-of-nowhere airport, or the flight itself.