Why? What makes Spacemacs so different/special that it requires some kind of distinct opinion that would be extremely valuable? Spacemacs is the same old Emacs with some out-of-the box customizations atop - there's nothing fundamentally different about it.
Searched by tags and found author may try Evil [1], but unsure if they followed through.
You're right Spacemacs is essentially a batteries-included version of Emacs.
[1] https://nullprogram.com/blog/2017/04/01/
Spacemacs "is not batteries-included" version of Emacs. You say that and people may get confused. It's not a "different version" of Emacs, it's not Emacs at all - it's an Emacs config you can configure - a meta config. It is more like a collection of recipes you can run on Emacs. That is an important distinction.
Hence my question, what Wellons (who's a seasoned veteran of Emacs) could ever say anything about Spacemacs (or Doom - which in this context makes no difference)? What kind of views one would be interested to hear? Using the Space key as the "Lead key", or something about local-leader key; or vim-navigation/Evil in general; or modules/layers architecture of Emacs config? He said in that post you shared that he believed he'd eventually end up using Evil - he doesn't need to use Spacemacs for that.
Spacemacs is great for beginners, for people who don't want to deal with learning Emacs native bindings - they are legit confusing. For someone like Chris, it makes little sense, they'd probably would just add modal editing packages to their existing config. Even though Spacemacs and Doom are still valuable - one can find many interesting gems there.
Also, these projects may give you a good discipline for structuring your keys mnemonically - everything files related would be at "SPC f", search stuff on "SPF s", etc.