Earlier quoted context omitted.
The thing is, Vimscript sucks. Using a more mainstream language would be great for a modern advanced editor. Vim has a ton of Vimscript plugins but I wonder how long it will take the Neovim community to replicate most of their functionality in Lua. I'd guess that not that long.
I’m pretty sure that the primary reason we don’t have more VIM plugins, despite many more emacs users, is vimscript being terrible. If vim had a more usable scripting language it would have easily surpassed emacs in plugins and more importantly, since plugins would have been more popular, vim would have been developed in a way to make it more extensible and nvim wouldn’t even be needed.
I think emacs having more plugins is a consequence of its design and philosophy, not the extension language itself. After all, emacs lisp is not the best language in the world and only a small group really knows it beyond the basics.