It's not about the commands. Names, whatever. I learned GNU and BSD command sets cold, names and obscura are not a problem. It's about the experience of using the thing. Everything is so insanely verbose, except when line-noise symbols are injected to break up the monotony, and the editing environment for actually using it is absolute garbage compared to either bash or zsh's emacs/vim modes. You are stuck writing long, complex (not complicated, but complex) commands that can't be easily factored down, with an interface that isn't doing much to help you (and isn't good at the little things besides, ISE is unacceptable compared to a decent terminal emulator like iTerm2). And so iterating--exploring your problem space is unreasonably difficult compared to everybody else in the same space.

A shell is a REPL. If your language makes actually writing things in that REPL hard, it is definitionally bad at Shell Stuff. I find it significantly easier to write code in C# and then transliterate it to PowerShell than to actually write PowerShell. That's a disastrously bad situation for a shell.