> Occam's razor would point towards some general misunderstanding on which we have no evidence to reasonably speculate a cause.
Dark matter is the Occam's Razor theory. It explains almost all of the observations while assuming the least.
Why do you assume we have no evidence just because we don't have direct observations? Black holes were a similar phenomenon that we had no direct evidence for a fairly long time even though we had lots of other indirect phenomenon that really couldn't be explained any other way.