When observations don't match predictions, it used to be considered as possible evidence of falsification.

What if accountants could just write in a figure and call it dark money, whenever they find a gap in the books? (Oh, wait, that seems like usual practice these days.)

Has there ever been any effort to go back and consider the underlaying theory? So far we have Inflation, Dark Matter and Dark Energy to fill various gaps in the current cosmology.

As for Dark Energy, if cosmic redshift is an optical effect that compounds on itself, that would explain why the rate goes parabolic.

The Big Bang will prove to be the cosmologists version of string theory.