Of course it can be used. But it is very buggy (as in missing or not well-though-out behaviors), which is unlike the typical polish Apple human interaction folks deliver. For example switching between Spaces and then between apps and windows and creating a new app window don't work as expected in some combination of steps and for some apps. There are several other "corner" cases that show the features were not laid out in a full design to exhaustively decide the desired behavior in each case. Which is very much like when someone bolts on a feature to a system without fully nail down its interaction with all other adjacent and relevant features.

I'm just responding to your "Why would you use that feature?" question. I use it because I like it, and it works well for me. I'm not disagreeing that they have some bugs and design issues to work out. It seems pretty obvious MacOS doesn't get as much attention as iOS when it comes to these things.