The UNIX philosophy of "do one thing, well" and "write many programs that work together" is contrary to powershell's idea of having all the tools you need as built-ins to your shell. The minute you need something that the "one development team" hadn't thought of, or decided wasn't important enough to ship, you have to either port it to powershell as a plugin or write something more complex to handle your workflow. For all it's cruft and baggage, the fact that there's not "one way to do things" and is continually expandable is part of what endears UNIX to it's users.
The fact that PowerShell needs modules to fully work with something is definitely an issue - we'll have to see whether people start writing the modules to make PowerShell fully functional on *NIX. You can call existing command-line tools, or methods from the underlying .NET Core installation, but those are really just work-arounds.
To be fair, every programming or automation platform has that issue: Python and Ansible succeeded because people did like the basic systems enough to write code to extend their usefulness.
