If their calculations are right, then the presence of dark matter is not required to explain the internal motion of galaxies. This says nothing about the way they move wrt each other. It just weakens the argument for dark matter a bit.
But see below the article posted by moonman62. It seems that previously dark matter was well accepted as contributing to galaxy rotation so the jury is still out. This is just one result. It needs to be confirmed.
That’s my take as well. The result enables ordinary matter to explain intragalactic motion, but not intergalactic motion and other big-scale phenomena.
If, as the article indicates, the current dark matter model is intimately tied up with intragalactic motion, that would seem to rule it out for everything else as well.