Other people have already gave many examples, but they can all be summarised as "shorten the feedback loop". CI/CD shortens how long it takes to see your code

Other people have already gave many examples, but they can all be summarised as "shorten the feedback loop". CI/CD shortens how long it takes to see your code running in a production-like environment. A good type system and a good test suite help catch bugs before the program is actually run. Short compile times (or an interpreter), hot code reloading, a good debugger, all help to see the impact of your changes faster. Even autocompletion or an efficient editor like Vim relate to getting your code done and running faster. It all comes down to fast feedback. Reducing friction is also nice, e.g. PHP is really easy to get started, but not as important as the fast feedback IMO.