Even with ~300 posts and ~100 drafts it only takes 2 seconds to see auto-reloaded updates when I'm actively writing. That's within WSL 1 too (room for speed improvements are there with WSL 2).
It also has nice plugins to process SCSS and bundle your CSS / JS, along with md5 tagging all static files for cache busting without having to use Webpack or do anything complicated. You just reference them using a specific plugin's template tag. But at the same time you can choose to use Webpack if you'd like.
I'm not sure why the author mentioned Jekyll is too restrictive. You can write plugins to do some pretty custom things. Like, I wrote a few lines of Ruby to parse out time stamps from a list to make them clickable links so that I can jump to that position in a custom audio player, very similar to how clickable time stamps work on Youtube. You can pretty much do anything.