If keyboard is your main instrument, then I'd submit you should be fluent in at least half the keys, and reasonable in all keys.

Just because I can throw a frozen pizza in the oven, or fry a hamburger patty, or boil noodles, doesn't mean I can call myself a cook. If I have a few definite great specialties, and can reasonably prepare a large variety of other things; then I'll call myself a cook.

I think there are a lot of people who are too free using the words Professional Musician", and I know without doubt there are far far too many people in the music biz who refer to themselves as "artists".
Rather elitist? Maybe, but that's how I see it.