Well, they are used frequently and not just on these boards. The term “cafeteria catholic” is strongly pejorative, only used by the ultra-conservatives.
“Conservative” is a very bad word to describe a Catholic because it implies some sort of sliding scale continuum from conservative to liberal. There are only really two types of Catholics: orthodox and heterodox, or faithful and unfaithful.
Say you are a sedevacantist. That would make you, most likely, an extremely conservative Catholic. Your rejection of papal authority would, however, put you in schism with the Church. You would therefore not be a faithful Catholic and therefore not orthodox.
On the other hand, you might prefer the Novus Ordo mass (if done with due reverence) and hence you would be a faithful Catholic, but not a faithful Catholic traditionalist (aka Traditional Catholic). However, if you assented to all of the Church’s teachings, while you could technically be called a “liberal” by some (only in matters of practice), you’d still be orthodox. Of course, the label “liberal” is almost always used to refer to heterodox Catholics who are liberal in their opinions on matters of faith and morals, and not necessarily of practice.
To answer your original question, the unfaithful Catholics are possibly slowly beginning to lose ground as a proportion of those who self-identify as Catholic, many simply because they cease to identify as such. The older ones are slowly dying, and their corrupt faith has little in the way of substance, which means it is rarely passed on.
While the faithful, orthodox element may slowly begin to increase in proportion to the whole mass of self-identified Catholics, it’s unclear how much attrition there may be due to the pressures of secular culture, so their numbers may be decreasing, but at a slower rate. As faithful Catholics tend to be more evangelical and more concerned with passing their faith onto future generations, it is possible their number may remain stable or increase.
