That is a stimulating thought experiment. So the center of galaxies , the collective gravitational forces of objects orbiting that center will tend to cancel out, leaving a net zero remote attraction of zero , like the eye of the hurricane. But the orbiting objects close and far, are all following space-time curves, shaped by mass, that we call gravity. At the center therefore, the curvature is the most bent. And we have just said that the orbiting masses roughly cancel out at the centre. At our centre, the , a large mass cause that intense spacetime curvature. Mass tells spacetime how to curve, spacetime tells mass how to move.

A galactic centre cannot both a zero average, and a cause of high space-time curvature. There has to be a reason why it is a center of galactic rotation, and that is a concentration of real masses.

The Newton approximation, says the fall off in measured attraction force is inverse square of distance.

At a distance from the galaxy, the collective curvatures both decline and merge. While close to massive bodies, the nearest mass effect predominates. If a gravitational attraction point exists, absent of matter initially, then it would tend to attract and accumulate matter with time, a process that helped form planets and stars, clusters, and galaxies.