There are already some "vi" modes available in the standard Emacs; I know that vim-mode and viper-mode have been available at various times in the history of GNU Emacs.

There are three or four major add-ons to GNU Emacs that will completely change both the appearance and the default key mappings, while not eliminating them altogether for those who may want to use them on occasion or go back and forth. Doom Emacs is one very popular option; Spacemacs is one I’ve been using recently, and as I mentioned, there are others, which interested individuals can explore for themselves.