> It fits the data extremely well. That is the proof. It explains many unrelated phenomena and isn't ruled out by anything;
Suppose you had six frames of a ball moving in a parabolic trajectory. A sixth order polynomial would fit the data incredibly well, but I don't think you would accept it as a good model for the motion of the ball.
You can't say "it isn't ruled out by anything":
EFE rules out LCDM.
Galaxies are redshift >~ 7 rules out LCDM (we now have galaxies at redshift > 13).
Suppose you had six frames of a ball moving in a parabolic trajectory. A sixth order polynomial would fit the data incredibly well, but I don't think you would accept it as a good model for the motion of the ball.
You can't say "it isn't ruled out by anything":
EFE rules out LCDM. Galaxies are redshift >~ 7 rules out LCDM (we now have galaxies at redshift > 13).