In my experience the problem with Scrum is that people are not able to implement it correctly. So maybe it's biggest flaw is that is not easy to understand for

In my experience the problem with Scrum is that people are not able to implement it correctly. So maybe it's biggest flaw is that is not easy to understand for the people who has to follow it... But I have to say that once I had a really good scrum master. He was extremely strict with telling the product owner and so on that a story can't go into the sprint if it's not 100% ready and also telling developers to not accept one story too much if they are not completely sure to finish within the sprint. What happened is that product owner and other business people didn't like this guy because they felt he was stopping progress, but from my point of view, before him they were running in circles reworking the same features with things they forgot but they didn't realize. I felt totally the opposite. As a developer I was always finishing all my tasks without stress and high quality, reducing the amount of bugs and forgotten features, and I had time to help other teams, for instance the product owner himself, to complete their tasks better. Guess what: This scrum master was an ex-developer