In general, I think people really sell themselves short by using an editor "distribution." It's a "teach a man to fish" situation. The whole point of being able to configure Emacs or Vim is so that each person can make it into the tool he or she wants it to be. That's sort of why I recommend Vim as an IDE[1] to people. It teaches people how to configure Vim for themselves, so they can better understand how the pieces…
Since I switched to nvi I've learned way more about the powerful features of the base editor as well as shell tools like grep, fzf, fmt, column, wc, expand, pdftotext, pandoc, make, git... With tmux I have easy access to any REPLs and man pages I need. The main feature of nvi I need over the original vi is unlimited undo, though ex command history and file name completion are nice as well.
Part of the inspiration for me to switch from vim (and spacemacs) down to nvi was this post on stack overflow [1]. When I really grokked the power of this system I picked up O'Reilly's book on vi and vim [2] and read every page of the vi and ex stuff. There is soooooo much you can do with this editor that doesn't require plugins yet people reinvent them, often in a less powerful/flexible way.
Since learning to be productive in nvi, it's going to be very hard to go back to those bigger, more extensible editors. The temptation for bikeshedding is too great... Oh, and learning to read code with syntax highlighting turned off is really nice. It helps you write more clearly since you aren't relying on the highlighting to help the reader.
[0] https://sites.google.com/a/bostic.com/keithbostic/vi/
[1] https://stackoverflow.com/questions/1218390/what-is-your-mos...
[2] https://shop.oreilly.com/product/mobile/9780596529833.do