You need to check your sources again. Because gravity has literally EVERYTHING to do with the motion of the Milky Way and all of the other galaxies, as well as the motion of all objects within our own star system.
What exactly are you suggesting planetary motion is derived from? 
I am referring to the knowledge of ancient Stories of Creation and of course I´ve checked my sources and compared these with the thinking of modern cosmology.
The ancient stories of creation deals specifically with the formation of out Milky Way and NOT of the creation of the entire Universe. The beginning of these stories looks very much as in modern science:
"Rivers of primordial matters flows together in a swirling center" and when heated up, a central light
(Electromagnetic Force) is turned on and began to create firm matter and fluent spheres of gaseous elements.
The BIG different between ancient and modern science in this case, is that the modern science just have a random and not localized "cloud of gas and dust, which come together", whereas ancient knowledge locate this cloud as the beginning of the Milky Way and the very formation of it and everything inside it, of course included our Solar System.
That is: All rotational and orbital motions in our galaxy derives from the swirling momentum in the Milky Way center, caused by an attractive force in the first place and after the formation and spreading of starry spheres in the galactic center, these starry spheres are repulsed away from the galactic center and out in the galactic surroundings.
That is again: We are dealing with BOTH an atractive and repulsing force of creation and Newton would have concluded this from his studies of ancient cultures, but he didn´t understand and grasp this. In stead he came up with just half of the story of creation, the attractive part of it, which he falsely ascribed to the whole part of the creation.
This was why his ideas was discarded by Einstein and this was also why his ideas of universal celestial motion was contradicted by the discovery of the galactic rotation curve, which de facto describes an outgoing motion from within the galactic center and outwards in the galactic surroundings - just as the ancient Stories of Creation states.
The formation of our Solar System:
As mentioned above, the pre-Solar System starry sphere was formed in the galactic center and on its way out from the center, planets were formed out of the swirling and molten hot Solar Sphere and later on the planetary moons were formed out of their mother planets and ALL rotating and orbiting motions are originally the results of the swirling motion in the galactic center from where the Solar System was formed in the first place.
This outgoing motion from the galactic center is STILL at work as increasing distances between the Earth and the Sun and also between the Earth and the Moon.
My conclusion: Modern cosmological science has everything to learn from the ancient Stories of Creation and unfortunately Newton missed this knowledge and began to put the little he knew onto mathematical calculations, mostly based on pure speculations and with NO causal explanations at all.
