This is not even in the same ballpark as "oh look here's a single star which seems to be dimming in a weird way."
How do you know that? I think there was earlier little things that have destroyed entire systems of thought. (I do not have a reference.)
I think that these problems are all not shown up at once,
observed galactic rotation curves, the velocity distribution of galaxies within clusters, the gravitational lensing by clusters, the formation of the cosmic web, and the rate of change of the expansion of the universe according to the Friedmann equations.
but have little by little accumulated.