We're not a startup, but what helped us nail delivery down is actively choosing between releasing feature sets or releasing on a schedule. You can't realistical

We're not a startup, but what helped us nail delivery down is actively choosing between releasing feature sets or releasing on a schedule. You can't realistically get both. If you can, having a rolling release every two weeks that includes everything that's gone through Q&A means you have constant progress, no matter how slow it is. The other end of the spectrum is digging your head down until you get a set of features out and doing a release once that's done. Having constant rolling releases relieves your team of a lot of unnecessary pressure and is also a roundabout safeguard against feature-creep. I'm aware it doesn't work for a lot contexts, but if you can make it work, it's great.