It's strange. I have used Ryanair on various routes over the years. I think all were heavily loaded, if not all seats taken, and certainly not at their supposed bargain basement fares.
Yet, with the singular exception of London Stansted to Dublin (whose frequency itself is well down on past years) all of these routes I took have gone. Extraordinary. Meanwhile pretty much all the legacy routes I have taken over time carry on, often with improved frequencies. You certainly could not plan business branch foreign offices or a holiday home on the basis of Ryanair routes.
The selection includes :
Prestwick to Stansted
Stansted to Tampere, Finland
Stansted to Kos, Greece