The Spacemacs creator took a long break at some point and never really handed over the reins at least while I was using it. I don't know if that has since changed (I assume it must have) but that was a big reason why I switched, together with its slow time to start-up.

Doom Emacs launches incredibly fast and has a ton of modules you can flip on and off to get a great Python development environment or what have you.

Same for me. I wonder what has changed in Spacemacs in the last two or three years? Is there anything that Spacemacs offers that is non-trivial to do in Doom?

Try it out, it’s so much faster and more actively developed compared to spacemacs. Chances are you’ll love it. The community is very active on discord and discourse. There are roughly 2000 users on each platform. Doom and emacs in general has seen an uptick in the last few years (anecdotally). Doom is such a wonderful project, with an excellent maintainer (hlissner).

Similar project to Spacemacs, doom-emacs seems more alive recently, some people say it is faster than Spacemacs. I like both, but I never switched to them from vim.

When I switched to doom several years ago was the last time I declared startup bankruptcy.

Similar, less included in the distribution. Doom to me generally feels a little more opinionated but easier to reason about.

They’re both quite good at what they do, and they do similar things.

As others have said, Doom seems faster than Spacemacs, especially at startup. Doom has lighter weight config, but it's also less opinionated. I've been using Doom for a while now, and the only thing I missed was Spacemacs' keybindings. Those can be recreated in Doom though[0].

[0] https://github.com/chenyanming/spacemacs_module_for_doom

Maybe give https://github.com/bbatsov/prelude a look too, if you haven't already.

It's a bit more minimalistic, while providing a rock solid base on which to build.