I disagree with that definition of news. Keeping politicians accountable is certainly one of the functions of the press, but there are a lot of possible news items that don’t refer to politicians. “Winter storms hit [location]” is news, but not related to politicians unless it talks about steps local politicians are taking to prevent storm damage (which is not necessary for a good article). Or “Physicists find [particle they were looking for].” That one could be in Science rather than here, but it is definitely news, and I personally think it’s hard to shoehorn politics into a discussion of particle physics without losing track of what actually happened. Very few politicians involve themselves in that kind of research (though, to be fair, it might be news if they did).
Whether it’s possible to have a purely apolitical news forum is a different question, and I am sure it’s possible to put a political spin on almost anything if you want, but I just don’t think it’s true that news must be political to be news.