There is no one definitive answer to why Cartoon Network stopped airing their old shows like Ed, Edd n Eddy, Courage the Cowardly Dog, or Dexter's Laboratory. However, it is common for TV networks to rotate their programming to keep it fresh and attract new viewers. Additionally, networks may shift their focus to new shows that are performing well or that are more popular with their target audience.
As for which channels rerun old Cartoon Network shows in English, it can vary by country and region. In some countries, these shows may be available on streaming platforms like Netflix or Hulu, while in others, they may air on networks like Boomerang or Adult Swim. It's best to check with your local TV listings or streaming platforms to see what options are available in your area.