A) Knocking down Thanos is not the same thing as hurting Thanos. Was he woozy? Did he have a hard time getting up? Was he damaged in any way? If Thanos was not harmed, the attack was clearly harmless.
B) Thanos was dragging out the fight against Earth's heroes to make it more dramatic for Death. This is explicitly stated on panel and reinforced by "no duh" logic.
C) It's fair to say that Thanos stalemated against WM Thor before he got sick of fighting. There is no convincing evidence that either was "losing." That should make it clear how far above Thor Thanos normally is--Thor needed Warrior Madness AND the power gem to stalemate him. That's totally reasonable.
D) The times Thor has fought Thanos while not amped, he has gotten completely, easily owned. Period. He would be dead at least three times now without plot-twists to save him as Thanos stood over his kicked-butt. Go read the times Thanos fought the Avengers.