I also jumped ship to AstroNvim but I still prefer Lunarvim, I liked having all the config in just one file and some of its defaults. But I agree, Astro is the best distro currently maintained distro in my opinion.
You can definitely put all of your configuration into a single file for AstroNvim if you want.
In the docs it shows the minimal configuration to get AstroNvim running which is <10 lines in your ~/.config/init.lua file and then anything else you can just drop in that same file if you want. (https://github.com/AstroNvim/AstroNvim?tab=readme-ov-file#mi...)
One file worked fine until it didn't. At one point it was 500+ lines and became unwieldy to manage.
Though I might one day switch to Zed or Helix -- I want an editor that has more bells and whistles built-in and that I could just switch them off if I don't want them. Which should be a much smaller configuration footprint compared to what we have today with Neovim.
