[YPPH]

That's kind of trivialising it. It's usually more complicated than dropping scripts on instances.

Unless you're doing something very simple, there's a lot of wheel-reinvention involved in writing your own scripts when there's mature software and services available to manage infrastructure at scale.

And what you've said doesn't really address networking, storage allocation, and the many other things the cloud provider handles, which is not configured on the instance, but rather, by vendor-specific APIs.