See what fellytone84 had to say about keysnail, here on HN, 4 years ago [2]: I consider Mooz's Keysnail Firefox add-on to be the most impressive keyboard oriented browsing tool. It's endlessly configurable, dotfiles in javascript--really nice to work with. For Chrome, the Vimium extension is very good, but recently I've been having a lot of fun with a similar, more configurable alternative called chromium-vim.
[0] https://chrome.google.com/webstore/detail/cvim/ihlenndgcmojh...
So while I do miss the old extensions, and disagree strongly with how they went about it, any particular thing that's available only on chrome isn't really because chrome is better. With a little push cVim could support both browsers.
There's also a menagerie of Vimperator alikes for Firefox: Tridactyl, Vim Vixen, Surfingkeys, Vimium-FF, VVVimpulation. Most of them have improved substantially since September 2017.
Disclaimer: lots of Tridactyl's jank is my fault.
The new versions of Firefox have almost the same plugin interface as Chromium. If you're satisfied with it, then why aren't you satisfied with it?