Stelvio's main selling point here is that you can use our higher-level components for different services and have them automatically configured.
So, you don't have to configure IAM roles, or Env vars manually, as this is handled for you through a concept called linking. https://stelvio.dev/concepts/linking/
In our experience, that alone adds a lot of productivity gains for teams.
Higher level CDK constructs do the same thing. But honestly, IAC is one of the easiest thing for LLMs to do and there is plenty of documentation to troubleshoot. There is no reason to introduce this into a company instead of using the official CDK.
Why not use CDK L3 constructs (patterns) or the corresponding for Pulumi, since that's what you generate?