How was technical debt not one of the things mentioned? In my experience that’s by far the #1 reason for poor velocity.
My target audience is founders of very early-stage startups, so I cut the section under the assumption that they probably won't have much technical debt yet.
Early-stage startups tend to have rampant technical debt for two reasons:
1) They need to get a product to market immediately and they need to iterate on it rapidly—so using technical debt as a tool to achieve short-term goals quickly is actually awesome.
2) Startups tend to pivot. Making fundamental domain changes to a product quickly tends to give you very weird systems, often with large unused portions.