I have delivered successfully projects using Scrum, but we were fortunate that our Scrum Master was well trained and a senior engineer. Our CTO also let us figure things out, and helped us when we were blocked. He was genuinely concerned with the team having a balanced workload, ensured we deliver user value and our software was of high quality. Story points were not used as performance metrics but a tool to help provide stakeholders with some estimation, but only when our velocity became stable. Overall, our process was light-weight, we spent most of our time coding, and we pushed hard to deliver value to the user. If we fell short, we learned from it, no blame, just learned.