Patrick Bamford's 14th goal of the season in the 31st minute and an excellent long-range finish from Ben Reeves five minutes into the second-half sentenced Wanderers to a second successive defeat for the first time this season.
They have now taken just four points from their last four games and an angry Jackett said: "It was a disappointing day and I don't think we showed enough appetite and desire. We didn't match the motivation levels of MK Dons.
"Our start to each half wasn't right and our appetite just wasn't there, which it usually is.
"We have to use this as a lesson. We have just lost two games on the trot for the first time this season and we have to bounce back.
"We have to start by competing and play with hunger. We have to play with determination, we have to run to close down and make angles more than we did today.
"Our standards have been higher than that and I think that the standard the players are capable of are higher than that.
"We can, and have to, play better and play with more appetite.
"I can't say that we did enough to get something out of the game.
"I just felt as a team we lost appetite and that is why we lost. The opposition had more appetite than us."