I'm sure the author means well but I can't take any "guide" that starts out with Homebrew seriously.
I will tell you right now that it is not "essential for any developer", unless you want to start a debate about the meaning of 'essential'.
It seems to rely on Homebrew to set up all the other pieces which is, on my book, a hard no. The suffering I see in my org with Homebrew's reliance on pyenv (it only provides 3.9 - Big Sur provides 3.8 and all the rest is via pyenv) is enormous. I have moved to MacPorts for most of the stuff I need and it makes the machine a lot more like a straight BSD-based Unix, with the added benefit everything can be removed by an `rm -rf /opt`.
So many people use Homebrew now, though. Even Google uses it.
Another problem I see with this guide is that it seems a little dated, especially how it assumes you're going to install Alfred instead of using Spotlight, which keeps getting better and better with each macOS update and is almost feature-full enough to forget about using Alfred.