Unix shells are quite good for their purpose. It's not a full-featured programming language. Can you explain what is "poor man's REPL"?
> Pipe based interactions work properly only across CLI based applications
Yes. If you want to find something in logs or looking at any other text data pipes is a good solution. In any other case(like binary data) it will be better to choose GRPC(or any other RPC). I never have seen GUI apps on servers, sorry.
> PowerShell or other Xerox inspired shells don't need kernel support to achieve their workflows.
Good for them :)