Really?
Does the number π (pi) exist? Are mathematicians correct when they say that, for every map, a four-colour colouring method exists? Does the play
Romeo and Juliet exist? Does the wind exist? Does gravity exist? Does an electron exist? Does the Universe exist?
Who, exactly, uses your definition of "exist"? A Google search finds that it only occurs in your post here on CF.
I see that you believe it, but shouting doesn't make it true.
Gravity is more than just a concept. If you don't believe me, try jumping out of the nearest window.