Even Wikipedia article [1] on the rotation curves mentioned that those could be explained if one stops using Newtonian mechanics and rather try to use the full equations of General Relativity. Basically it turned out on the galaxy scale one could not use Newtonian approximation. GR equations are highly non-linear and even tiny non-Newtonian effects accumulates.

Then there are various articles pointing out that taking into account that galaxies are filled with plasma can also explain observed results.

[1] - https://en.wikipedia.org/wiki/Galaxy_rotation_curve