The Hoops suffocated Barca in their meeting at the Nou Camp on Tuesday, eventually losing 2-1 after Jordi Alba's injury-time winner, but Schuster was not a fan of how the Glasgow giants went about their business.
"I'm fed up of seeing these type of matches," said the German.
"You see Celtic defending with ten men and almost snatching a point - that is not fair."
"He decided to repeat the system, but the ultra-defensive system is not football.
"UEFA needs to change this phase of the competition if they want to breathe life into the Champions League.
"Celtic do not merit their place if they are going to play in this style."