I think that these 'improved shell' projects (incl. crush and nushell) that try to copy powershell somewhat miss the point of the shell in the first place. If I want a high-level language that's tightly integrated with the unix environment, I already have perl and tcl. Little more power (maybe less integration, but greater capacity to build new integration) and I can use raku or lisp. The point of shell is that it interoperates freely with all programs and all programs share a language. If now, suddenly, I can only use commands that have been explicitly rewritten to support your environment; or regular commands are second-class citizens and need support code to interact with your environment's higher-level functionality——
Then your environment is useless to me. Because I have better programming languages which, despite being able to interact with the system and its commands, don't pretend to be one with the system. As a result, the core high-level language constructs mesh better, because they're not trying to serve two goals at once. It's not possible for something that's not a 'real' shell (including fish, zsh, even csh) to integrate with the system the way a real shell does, because the system itself was designed around the shell.
Then your environment is useless to me. Because I have better programming languages which, despite being able to interact with the system and its commands, don't pretend to be one with the system. As a result, the core high-level language constructs mesh better, because they're not trying to serve two goals at once. It's not possible for something that's not a 'real' shell (including fish, zsh, even csh) to integrate with the system the way a real shell does, because the system itself was designed around the shell.