It's literally automatic by configuring your workflows by file changes.
> If you make your deployment fast and seamless, who cares?
It still costs CI/CD time and depending on the target platform, there are foundational limitations on how fast you can deploy. Fixing a button in a React SPA and deploying that to S3 and CloudFront if fast. Building and deploying a Go backend container -- that didn't even change -- to ECS is at least a 4-5 minute affair.