I feel the lisp constructed on top needs significant language expertise. Lispy constructs of defvar, defconst, defcustom, alist, cl-loop etc. are quite extensively used in emacs - and need an understanding quite unique to Lisp. Of course, the domain then builds on top of this shared understanding of the contructs themselves.

I would say that loss of expertise in emacs-lisp is a significant loss, even if there continues to exist C-expertise globally.

There's a wealth of packages and the documentation for emacs-lisp is quite extensive. It's not some esoteric language. But what I'm talking about is that the code for the packages can be quite simple and readable.