Problems of the Galaxies

The Newtonian and Einsteinian theories are often praised for their "astounding" predictive power, yet are unable to explain the motions and movements of the stellar systems of the universe.

Galaxy Uniform Cohesion
Galaxies are observed to spin as if they were solid disks, but according to theory, the center of the galaxy should be spinning much faster than the edges. In order to explain the rotation of galaxies modern astronomers need the entire galaxy filled with some kind of substance which holds the stars strongly together.

See http://news.softpedia.com/news/Stars-escaping-out-of-the-Galaxy-17222.shtml

Galaxy Rotation Rate
In addition, Galaxies as a whole are observed to spin too fast for their alleged size, beyond the point where, according to theory, the stars should fly away from each other.

https://www.dummies.com/education/science/physics/the-universes-dark-matter-and-dark-energy/

Distaste of the Scientific Community
From https://www.quantamagazine.org/troubled-times-for-alternatives-to-einsteins-theory-of-gravity-20180430/ we read: