Could it be, nevertheless, that Einstein's theory is wrong? Might it be necessary to modify it—to find a new theory of gravity that can explain both the stronger gravity and the apparent antigravity being observed today—rather than simply throwing in invisible things to make the standard model work?
A much faster speed of light in the infant universe solved the horizon problem and therefore explained the overall smoothness of the temperatures of the CMB radiation, because light now traveled extremely quickly between all parts of the expanding but not inflating universe.
Hunting for elusive dark matter is now a multibillion dollar international scientific industry.