To borrow a definition from Andrei Konchalovsky, art is that which imparts feelings. If a game does that, it's art. Many "gamey" games don't, and this is perfectly fine.

Consider two games, Inside (a great art game) and Overwatch (a great "gamey" game). Inside is much less rich in terms of gameplay, but (in my subjective opinion) does much more with feelings. Overwatch, on the other hand, is enormously, ridiculously rich in terms of gameplay, but when you're actually playing it (as opposed to viewing the art), it's more of a dopamine binge.

There’s not a strong definition and most attempts end up defining regular games as well. So it’s more a self label of intent by the creators.