Spacemacs uses “Evil mode”[1], which is available just as a regular (MELPA) package. I started with Vim and so I’ve always used evil. “Vanilla” emacs, spacemacs, now doom.
I'm curious if you've already used evil with vanilla why you'd migrate to spacemacs or doom. I've never found either to add much that a custom config can't get to easily and with more control. Maybe that's changed in the past half-decade or so since I last tried Spacemacs, though.
The vim bindings are only one part of Spacemacs. The other (and I'd say most important) part is the SPC menu that exposes hundreds of keybindings in a discoverable, unobtrusive, and interactive interface.
The keybindings are bound with evil and displayed with which-key, but the spacemacs special sauce is the keybindings themselves. There are probably thousands of them across all the optional layers. They're crowd-sourced essentially. So you don't have to set them up manually for each language/tool you work with, you just add the layer and get sensible defaults out of the box.
I guess so? And if the aim is to make something completely custom, that's fine. But the Spacemacs keybindings are very well thought out, the configuration is just as important as the feature itself.
I have a somewhat lengthy vanilla config, and I can tell you why I'm thinking about trying out Doom:
At work, I had to make some simple modifications in a go project. I've never done go before, so I had to google how to add support for it on emacs. There's always more than one choice, which one is the best maintained package? Is there an optional but ubiquitous plugin that will make it more enjoyable?
With Doom, you just add the go layer and you're good to go. I'm fine spending time setting up, i.e., a clojure config, since I use it all the time. It's well-spent effort. Not as much for a language I seldom have to use.