I received an article for review from a journal I did not review for before and honestly haven't even heard of so far. It is not a predatory journal, just a journal that until quite recently had a very narrow scope that did not overlap at all with my field of research. The article I was sent to review was within my expertise, though.
To get to know the journal I had a look on their website and from what it seems they recently expandend their scope to a more broader range of topics. Yet in my opinion, the article (which would have been totally out of scope previously) still did not really fit into the new scope either. This is why I wonder: Is it rude to tell the editor that I do not think the article is within the scope of their journal, because sorting out off-topic articles is their job and that would kind of critisize their work?