After losing to Colombia in the group opener, South Korea were upset 1-0 by debutants Morocco who are 55 places below them in the women's rankings.
The Englishman took over the South Korean team in 2019 and guided them to a runners-up finish at the Asian Cup last year.
But he said the squad had not done themselves justice at the World Cup while pinpointing issues which needed to be addressed.
"Our game is too slow. In Korea, there is no intensity or not enough intensity. The training sessions are too long and are not intense," a livid Bell told reporters.
"I have said this now for four years. I will continue to say it until everybody's sick of hearing it and we'll maybe, hopefully change. Because if you don't change, you will stand still and not progress."
Bell, who worked for years in German football, highlighted the changes the European country's football association made in 2006 to make them world champions in the men's game in 2014 and suggested the Korean FA should take drastic steps as well.
Bell added that Korean players are not mentally prepared as a league system without relegation does not give them a psychological edge when the stakes are high.
Losing and finishing in the bottom of the table has no consequences in the WK League where most of the squad plies their trade, he added.
"The playoff system for me, personally, is a system that is nonsensical and doesn't belong in football. You want to win, finish first. You finish last or second last, you get relegated - this is competition," he said.
"This is the reality, the World Cup is the reality. We have the best players, the best teams, the best coaches on view. If you lose, it hurts. If you lose, you get knocked out. That's the reality and that's happened to us.
"That's just more than a slap in the face and we've got to wake up to the reality of life. Life is sometimes difficult, life is sometimes tough. You have to live in reality, you can't live in a dream world."
