The Manchester City midfielder vented his frustration at the players and coach Domenico Tedesco's tactics after Monday's loss in Lyon.
De Bruyne complained a lot was not right with the Red Devils - third in the 2018 World Cup - who sank after a promising first 20 minutes.
"There were six of us at the back. Even in the second half when we were trailing it was like that," he told Flemish television VTM.
"It's our way of playing that is in question. There are players who did not fulfil their role, full stop.
"If you are not good enough, you still have to give everything, which some people aren't doing. I can accept that we are no longer at the level of 2018 but things are unacceptable."
De Bruyne was also filmed on the sidelines saying several times to technical director Franky Vercauteren "Ik stop" ('I stop') with the national team.
Belgian media reported that De Bruyne also made comments in the locker room that were hurtful to his teammates.
But Tedesco insisted he did not believe that the 107-times capped player was set to exit.
"Kevin is a winner, it's normal for him to be disappointed. But I don't fear his departure," said Tedesco.
Belgium are third in League A Group 2, level on three points with France, with Italy leading with six points.
On Tuesday, visiting a children's hospital in Brussels, De Bruyne said he had "slept little" but it was "neither the place nor the time to talk about football."
