Germany's 3-3 Nations League draw with England on Tuesday (AEST) meant it finished third in Group A3, having won just one of its six matches.
Its shaky recent performances and failure to reach the Nations League's final four have led to questions being asked of manager Hansi Flick.
But Boateng, who played 76 times for Germany between 2009 and 2018, believes fans should reserve judgement of the team until the FIFA World Cup is over.
"Shortly before the World Cup we have 80 million national coaches again," Boateng wrote in an Instagram story, alongside a laughing emoji.
"We have a strong team, we can beat any opponent and become world champions. We have young players in all positions.
"How about approaching the World Cup in a positive way and not criticising the team and bringing in unrest?
"Stay positive and support the team together. After the World Cup you can add your two cents again."