What does "keep [something] simple" mean? Does it mean that someone messed the thing up badly?

Native speaker’s answer
Rebecca
You might have heard of the sayings "simple is best" or "simplicity is key" before. It implies that the more complicated something is, the more room there is to mess it up or make mistakes. George made the process of making an apple pie very complicated as he wasn't very careful while making it, which caused him to create the mess you can see in the video. This is what the speaker is referring to when he says "well, you didn't keep it simple" here. Ex: There's no need to bake super fancy cookies. Simple is best. Ex: If you keep it simple, you can expect it to go well.