Well, while I accept the the theories of dark matter and dark energy at face value, I freely admit that I have missed something in the development of those theories. I haven't found what it is I'm missing yet, but from
my knowledge of physics, dark matter and dark energy is speculative.
I don't understand why the observations can't be explained by minor adjustment to the laws of gravity - perhaps an inverse nth power factor in there with the inverse square law which of course dominates at our more familiar distances. Hopefully one day I'll find the missing piece from my jigsaw so at least I can catch up!
Al.