I dont believe it is pilot training, but rather Ryanair doesnt always install proper lighting for heavy fog nor do the smaller european airports on the runways themselves. The lack of more advanced lighting on the planes is probably fine for major european airports that have ground lighting rated to a category of visibility, but the smaller airports have a lesser lighting and fewer backups so combined with Ryanair planes the pilots don’t/can’t risk landing. I had this experience in Poland, where a ryanair flight was expected to land in Bydgoszcz but landed in Gdansk instead (without informing anyone in English of what or where we were)