Andy O'Shea also pointedly points his finger at the 'selection' procedures used by ATOs. Ryanair find no difference in quality between modular and integrated candidates and he notes that where selection has taken place it has had no obvious filtering effect, otherwise one route would be obviously superior to the other. From an end users point of view it isn't.
You could blame the candidates for lack of maturity etc. but really one would expect ATOs to filter out the untrainable, politely decline to take their money, and then train the remainder up to standard.