If you use Emacs in Vim mode -- I'm not much of an Emacs user in general, but lately I've actually tentatively taken to Doom Emacs, much to my own surprise -- is Mastering Emacs still useful?
I’ve read some of Mickeys blog posts, not the book. I can generally recommend learning how to emacs and I’m sure mickey will help you a lot to do that.
I used vim for 5ish years. I switched to emacs with its C-p C-n etc for a while. Then I found found boon, then I made my patch to it. vim to me is now subsumed by a <1000 line hackable elisp file.
The whole process of installing the boon code, searching and navigating it, making changes and dynamically reloading it, and then using it, etc. You can take it one step at a time and everything is ready for you to take the next step.
In vim, it works the way it works and you can learn it and use it. In emacs, same, and if you want you can also easily browse it’s code and dynamically change it. It’s strictly better. Zen and the art of motorcycle maintenance
I also find that browsing the source is so easy that documentation is more annoying to use. Sometimes I find documented customization options that are the little hack i would have made in the code anyways.
It’s not everybody’s cup of tea, but it is truly a cup of tea.
Vim is a text editor, emacs is a text manipulator. If you never want to do more than copy a rectangle of text from region a to region b then you don't need more than vim. If you want to write tools that fit your workflow you need to know elisp.