You're conflating build times and deploy times. A low friction deployment might take a couple minutes end-to-end for something that "builds" in a few seconds once the CI is booted up. Sure, that's fine for hobbyist stuff that is always being edited by the web developer and nobody else. The point is a proper backend editing experience brings so much to the table. Once upon a time, my promotion was delayed because the team lead I answered to decided to use a SSG instead of a proper CMS, and non-technical stakeholders were not happy about the limitations.