The issue with alt tab and the main reason why I personally eventually moved into tiling managers is the reliability.
Alt tab often requires two things: 1) Figuring out how many clicks to away your desired window is, as they change 2) executing those multiple key presses correctly
When you compare this situation with a wm where you place or permanently bind certain windows to a number (eg messaging apps are always CMD + 0 for me) then you can see how you can grow to prefer the certainty, there's no more fiddling for the window you're looking for.
Windows actually sort of had this feature with windows + numbers as that focused the window by order on the bottom bar, but lately with window groupings and things like that it breaks for common use cases such as multiple browser windows.
How is this related to tiling managers if you can do exactly the same thing without them in your generic shortcut utility?
There is also a downside of this certainty: you always need to keep in mind the two recent apps you're working with (for some uncommon apps you wouldn't even have a predefined CMD+0) and then your CMD+0 wouldn't help if you have multiple messenger windows and need to switch between two