I suspect the Which? members are largely people of advancing years who hark back to the days of free meals, free bags, free seat selection etc and for the most part travel on legacy carriers that still offer some of these frills. They would only have to have one experience of Ryanair to realise the world isn't like that anymore but it wouldn't stop them complaining that everything is "wrong2 with Ryanair.
If their recent passenger figures and profits are any measure then they are satisfying the mass market end of the industry, and to be honest if I ran an airline as successful as Ryanyair I would take diddly squat notice of reports by the likes of Which?.