> emacs lisp is not the best language in the world
Emacs-lisp is a Lisp. It may not be the best of Lisps, but even a bad Lisp can be far more powerful than many other non-lispy languages. To understand what makes Emacs so awesome, one has to understand the philosophy of Lisp. Emacs Lisp is not just a text editor, IDE, email client, project management tool, scientific calculator, etc.
Emacs, first and foremost is a Lisp environment. Definitely not the most ideal, but certainly the best one we have today.
> I think emacs having more plugins is a consequence of its design and philosophy, not the extension language itself
I believe, Emacs held the crown of "the most malleable" tool for over forty years, specifically because it builds on top of Lisp.
Number of plugins is not an indicator. They also have to "play nicely" with each other. I just checked - I pull over four hundred Emacs packages in my config, including built-ins and dependency libs. I just cannot imagine any other IDE or text editor with 400 plugins installed. That's just not possible.