It's unlikely to cover the AWS API's with 100% certainty, and I don't want to spend time trying to work out the kinks, so honestly, I'd rather just use the AWS CDK and CloudFormation.
Co-Author here. As long as you have trust in the underlying API of the Pulumi resources that Stelvio creates on your behalf, we have a mechanism in place that let's you fine-tune every parameter if you like. See: https://stelvio.dev/concepts/customization/
Otherwise, you can stick with Stelvio's sensible defaults if you wish.
It's not unlikely, I guarantee it will never happen. Because that's not the point.
Point is to cover most of the common cases (with escape hatch for fine-tuning in special case) and make those super easy and short to do so devs can focus on code and not infrastructure.
It's standard higher level abstraction play of doing more with less (code and time spent).
Thank you for the feedback.