I've once created a profile with about 1500 lines of code for powershell, managing AD at work. It was great to learn, it's great for scripting and it's very intuitive (for me at least), I also liked working with objects.
I wouldn't use it on Linux though, I'm not sure how well integrated it is.
I'm using fish at the moment, desktop and server, and I like it primarily for the functions and the autocomplete

limited functionality as it’s not the full blown .NET

This is misleading to the point of being completely wrong

On Linux, you do not have access to Windows UI frameworks like WinForms, the Windows registry, and to System.Drawimg (because it is just a thin wrapper over Win32). Essentially the entire .NET standard library is available on Linux.

I would argue that .NET is actually better on Linux for some things (like web dev).

That said, I can see no reason to use PowerShell on Linux unless you are a .NET dev.

There are PowerShell cmdlets that do not work on Linux. Again, mostly stuff that talks to explicitly Windows services and sub-systems. But that has nothing to do with .NET at all. Also, path separators and case sensitivity is different on Linux. So, cross-platform scripting is a pain.

For a long time I used a super customized zsh setup. It was, unfortunately, crazy slow and regularly broke on updates. It had precisely all the features and behavior I wanted though. Like you say, zsh is very customizable.

Then I switched to tiling window managers and with that to the alacritty terminal. This made me value start up times and performance, as I was constantly opening and closing terminals. So I spent a ridiculous amount of time optimizing my zsh config to be as fast as possible. This is also what I used for a long time before correcting my ways.

When that device, my work laptop, failed, I had to set up my desktop for work. This involved setting up zsh, which I quickly realized was a lot of work. So, on a whim, I installed fish.

Oh my god. Not only did fish have nearly all the features I wanted out of the box, but it was easy to add plugins (customizations) in a performant way. Fish even had default behavior I didn't know I needed. And most importantly: it was crazy fast!

Since then I have never left fish. It is so much better than anything I had imagined. At this point I use way more default features as well, so I pretty much only add the tide prompt and zoxide. I also have a functions and abbreviations folder which is essentially my zsh alias collection.

The crazy part is really how much faster it is though. I really, really love it. And now they're rewriting it in Rust as well!