I find that many people who say things like this have never actually tried to boost their productivity on Mac in the first place. As someone who uses Alfred, Karabiner Elements, Keyboard Maestro, Spectacle, Omnifocus, and a host of plugins on fish shell besides, it baffles me how slow my peers are at doing basic stuff they do twenty times a day. Just set up a shortcut, it's trivial.

Not so trivial on Linux. The fact that the author considers Firefox add-ons (!) a Linux feature is a clear indicator they never even tried on a Mac and were enamored by Linux due to the lionisation in the particular subreddits they follow.

Kind of like here! Not that there is anything wrong with getting excited about something. Just don't make sweeping generalizations.

Also, a small tip: You can put your Mac apps and configurations in Dropbox and they will show up and work as you expect across your multiple machines.

One thing I sorely miss after switching from Linux to Mac is i3. Spetactle gets close, but something as trivial(?) as switching window focus with the keyboard I couldn't figure out a solution for... Can Keyboard Maestro do it?

There are a couple of automatic tiling window managers for MacOS, the most notable being Yabai (https://github.com/koekeishiya/yabai) and Amethyst (https://github.com/ianyh/Amethyst).

Yabai doesn't handle window switching on its own but it can use SKHD (https://github.com/koekeishiya/skhd) or any other application that can bind terminal commands to keyboard shortcuts such as Hammerspoon (https://www.hammerspoon.org) or BetterTouchTool (https://folivora.ai) or even Keyboard Maestro. The commands are context-aware of spaces and the placement of windows on the x-y plane so you can move between windows relative to their position on the screen.