I'm curious as to why you say that? This is a naive question, i have no skin in the game.
> Eshell is _not_ a replacement for system shells such as ‘bash’ or ‘zsh’. Use Eshell when you want to move text between Emacs and external processes; if you only want to pipe output from one external process to another (and then another, and so on), use a system shell, because Emacs’s IO system is buffer oriented, not stream oriented, and is very inefficient at such tasks. If you want to write shell scripts in Eshell, don’t; either write an elisp library or use a system shell.
And yes, I never managed to make auto-completion work really well in M-x shell (or eshell).
One possible shell env you might be interested in is IPython. It's a Python REPL with support for launching external programs, shell-like variable substitution and much more. Coupled with qtconsole it makes for a great shell-like experience. I was using IPython under Windows as my shell for awhile, before switching to PowerShell.
While I certainly understand where you are coming from, I have found that zsh may be more complicated, but less "weird" (i.e. it is more consistent)
However, zsh is tons of tons of special cases that may be mostly consistent, but without any clear concept which would allow you to remember or deduce solutions. When you are a zsh wizard you can be really productive, but it is a strange skillset that takes time to achieve and require constant refresh.
IMHO the closest thing zsh has to a "concept" is that if it takes too many characters, then there's probably a special case which - if you knew it - could solve the problem in a shorter form.
