Some journalists that specialize in a particular field become experts, but it takes time to learn. Journalists don’t have some secret way to learn faster than other people.
Journalists do get training in interviewing experts and writing. That’s what they should stick to. Just like we really shouldn’t pay attention to a celebrity’s opinion of an issue that they don’t have special training in, we really shouldn’t be paying attention to a journalist’s personal opinion- we should rely on them to talk to experts and convey information, but their ability to form an opinion isn’t any better than yours.