Thanks for the expanation. "... are called..." actually is a literal translation of the Chinese phrase.What do you find strange about it?
Using "are called" sounds as if you are introducing the expression "mass media" to people for the first time, and is a form of words commonly used with children; with adults it often sounds very condescending:
Chickens, sparrows, crows and eagles are called birds.
The only unusual thing about your sentence is the word "the", but here it is justified, because "mass media" usually takes the definite article and you have included all the major elements. If you had just said "newspapers", for example, you might need a different expression: "Newspapers are one of the mass media", perhaps.
That is probably better, but it depends on what information you want to convey. If people have heard of the term "mass media" but are unsure what it means, then it would be better to make "the mass media" the subject of "be":So a better way to put it should be " Radio, television, newspapers and magazines are known as the mass media. "?
I agree but add that dropping 'mass' or not might depend on the context, for instance if you are distiguishing 'mass media' from 'social media.'I think these days we generally tend to drop the "mass" and just use the word "media" on its own.
Hence the definition of (the) media in Lexico (Oxford Dictionaries): [treated as singular or plural] The main means of mass communication (broadcasting, publishing, and the Internet) regarded collectively.