> I mean we got relativity because of a minor discord with newtonian Laws. (the orbit of Mercury).

I don't think that's true. One of Einstein's test for General Relativity, using Mercury's orbit, came around 10 years later after special relativity was proposed, which is understood to be motivated by both Maxwell's equations and experimental results suggesting that the speed of light (electromagnetic waves) not depending on the frame of reference. General relativity (explaining gravity) seem to have been motivated by Newton's gravity not playing well with Special relativity (with mass being relative and all).

I understand the frustration with Dark Matter, but my understanding is that Dark Matter is a guess that is known to be incomplete. Scientists are shooting everywhere to try to explain the discrepancy in gravitational effects and some form of undetected matter is currently the best hypothesis (but not the only one). You say that "we accept 90% observation disaccordance", but the source of its effect is being searched for.

See:

- https://hsm.stackexchange.com/questions/622/what-was-einstei...

- https://en.wikipedia.org/wiki/History_of_gravitational_theor...

- https://en.wikipedia.org/wiki/Tests_of_general_relativity

Edit: formatting, updated links