Perhaps a liberal application. But certainly you can say that of most any church or religion. Catholicism is not considered a cult very often, because it is so large. Just like Baptist or Pentecostals.
Definition of cult from Websters:
Definition of CULT
: formal religious veneration : worship
: a system of religious beliefs and ritual; also : its body of adherents
: a religion regarded as unorthodox or spurious; also : its body of adherents
: a system for the cure of disease based on dogma set forth by its promulgator
a : great devotion to a person, idea, object, movement, or work (as a film or book); especially : such devotion regarded as a literary or intellectual fad b : the object of such devotion c : a usually small group of people characterized by such devotion
The original meanings were 1 and 2 above. Over time the application was more towards the unorthodox (heretic), and often based on the church being small. Too big to be a cult! (like the Too big to fail thing in economic circles).
Indeed cult has become a pejorative.
Yet the Bible says the way is narrow. Who knows how narrow? As I used to say to my Brother, "Brother, we might all be going to Hell if it comes down to perfect doctrine. Because it is possible that there was one single church in the history of Christianity that got it right. That church lasted for 27 years in Medieval England. 273 people will be saved. The other 10 billion plus .. well, they should have know better."