Lewis Guy scored the only goal of the game after 35 minutes to condemn an injury-ravaged Dons to their first home loss of the season.
Robinson's men were booed off at the final whistle, and he said: "There were parts of that which weren't acceptable but what do the fans expect when we've got no David Martin, Shaun Williams, Antony Kay, Dean Bowditch and Stephen Gleeson? That's five of our starting XI.
"We've showed that maybe our squad isn't good enough - that's the big thing for me.
"I thought it might have been good enough but players didn't step up to the plate.
"The disappointing thing for me is that for 25 minutes we dominated that game - we passed it quickly and we had three or four gilt-edged chances that we missed.
"Then they scored and we completely reverted to almost a paused play. It was slow, across the back too much and we had wide players who narrowed off and didn't give us the space to play.
"The game-understanding from our players for the last 15 minutes was very poor.
"I've just said to the players in there that it's not acceptable and we've got to stand up and be counted."