Abstracting over cloud resources is inherently very leaky. Yeah, S3 compliant buckets work, but that's the simplest example possible. Even then, if you're working at scale, you still need to keep in mind features like (AWS) Intelligent Tiering, GET/POST/PUT costs, cross-region costs. This can be the difference between a 15k and 150k bill, you don't want to abstract over it. What's the point of a cloud language if I have to care about the specifics if I'm doing something at scale with it? I can just keep using Java or Python and the respective SDKs.
I don't want to write all of my stack in a cloud programming language. Especially one that is completely new and not cross-compatible with any other language. This isn't just a small thing -- it's a complete dealbreaker. There's no tools, no libraries. It's been a decade since Nim has started development and look at its progress now with so much interest behind it. Creating PLs and compilers follows the 80/20% rule.. it will take mountains of work to even make the compiler truly optimized and usable, and that's a basic prerequisite.
The cloud simulator is cool.. but there's already localstack which will simulate AWS services much more faithfully. If you don't have faithful simulation (and you can't do that for every cloud service), you can't use the simulation for anything besides playing around anyway. In which case, why not have a dev/testing environment and kill two birds with one stone? There's no point to unit testing cloud things, that's basically all integration testing anyway. You can unit test the code that interfaces with the cloud using the same language-specific tools that have always been used.