The problems Wizz have had to a degree is that they are not that well known as for example Ryanair are in Western Europe amongst people who are from the countries in Western Europe.
They are very well known amongst Polish people for example, both living in the country of their birth and in the UK, and also in countries towards the East of Europe, but their brand recognition outside this is nothing to shout about.
Ryanair benefit from having good brand recognition over a broader range of Europe and on the Polish routes. I've used both airlines quite a bit between Poland and the UK/Ireland and there is much more of a mix on the FR routes between Polish/English speakers compared to the Wizz flights being majority Polish.