Pietersen was informed by the ECB that his England career was finished in February following reports that the batsman had fallen out with key members of the squad and broken rules during the disappointing tour of Australia.
"Who plays for England is a matter for the national selectors and their decision was a brave one," Clarke told the Evening Standard.
"You select your captain, you discuss what that captain requires, what he's looking for. He has to decide what that team are about and what needs doing. This is about the culture of the team.
"Well, he hasn't actually had a particularly successful time since his runs in India (in 2012), not extraordinary. English supporters must move on. There isn't going to be any going back, that's for sure. That tour was a watershed."
Pietersen was named captain of Indian Premier League team the Delhi Daredevils on Tuesday.