Gundogan said the new format - set to take effect in 2024 and include a minimum of 10 games per team in the group stage - isn't much better than the controversial European Super League.
Gundogan's City withdrew from the Super League project - a 20-team competition that promised to give 15 clubs a permanent spot - after intense backlash from fans, pundits, and players Tuesday. Some of Gundogan's teammates, including Raheem Sterling, celebrated the club's decision.
"With all the Super League stuff going on ... can we please speak about the new Champions League format?" Gundogan wrote on Twitter. "More and more and more games. Is no one thinking about us players? The new UCL format is just the lesser of the two evils in comparison to the Super League ...
"The UCL format right now works great and that is why it's the most popular club competition in the world - for us players and for the fans."
Earlier this week, City manager Pep Guardiola blasted UEFA for looking after its own interests and denying teams recovery time between seasons.
"Do they listen when the managers and the footballers say when they want to finish the season and have two weeks, three weeks off?" he said. "And after, start again, start again. There are many injuries. What is the problem with injuries? Absolutely nothing. Another player, don't play this one, play the other one. The show must go on."
City, who are still active in three competitions, will play a minimum of 60 games this season.