In a game they simply had to win to have any hope of beating the drop, the Dons produced an ultimate no show as goals from Matt Derbyshire, Leon Best, Kirk Broadfoot and Richie Smallwood lifted the Millers nine points above the bottom three with five games to play.
It started badly with Derbyshire putting his side ahead after just 54 seconds and then it got worse, but Robinson insists the scoreline did not do his side justice.
"We were the better team in between the two boxes, by far. In the two boxes we are not as good as the rest of the teams, it's as simple as that," Robinson said.
"We are so close, and the scoreline does flatter them. It does, but if you don't put your chances away then that is what is going to happen.
"The league table says we are not good enough. I don't think it's a lack of effort or desire, that certainly wasn't the case. Right up until the last whistle we didn't stop, there was constantly people trying to run and keep going even when the odds were completely stacked against us.
"That's not enough to make up for the result, not the performance, the result. We have seen Jake (Forster-Caskey) hit two shots, the keeper makes a great save, one comes off the bar then they hit one of his shin and then it goes in the top corner. When things are going against you, it's hard."
The Millers doubled their lead before the game was even 20 minutes old when Best rolled in from the spot after Richard Wood was chopped down by goalkeeper Cody Cropper.
Robinson was infuriated by referee Iain Williamson's decision to award the penalty.
"It was a horrific decision, horrific. We have seen it a number of times and he has told me a bit of a lie that I am not too happy with," he fumed.
"I still can't understand how he has given it. The assistant referee has told me afterwards that he said, 'No penalty, no penalty', but the referee has had a better view. He was stood behind Darren Potter, how could he have had a better view?
"He couldn't wait to give it, he gave it so quickly it's ridiculous, without asking questions of anyone else. He clearly got the ball and pushed the ball away.
"These aren't excuses, I'm only telling you the facts of the game."
