Metaphorically it's a verb. It is the things you do or not. For example, fact check. The problem is, the belief that it's a noun and a noun one can assign to themselves; that has no formal definition.

If we want to user the word journalism / journalist properly and fairly then the easy way to do is to think of it as being a verb - like leadership. Leader isn't a title. It's actions you take. Just like journalism.