Have you ever heard the old saying "Don't burn your bridges"? It means try to leave all your relationships amicably, even if that means you can't really say what you want. When you quit job, maybe it's not the best idea to explain all of the very good reasons why that company is garbage. Maybe it's a good idea not to burn that bridge. Who knows when you might have to cross it again. Or you know what? Heck with that. Burn em. Burn all those bridges, and may they light your way to success.