It can't do the literal entire thing an operating system is supposed to do: manage applications and their resulting windows, in a sensible way.
I want to know what application is running.
Sure it's in the dock!
I want to find a specific application window.
Go fuck yourself right to hell.
Wait, the taskbar doesn't show the running windows, like it does on every other OS? It's at least discrete right?
It discretely takes up 1.5cm of the bottom of the screen at all times. It's so discrete it doesn't even need to use the corners.
Uh, alright, well that's all the system space you need right?
Yeah of course just that bottom inch or so .... And a top of screen system level menu bar to display what windows does in the bottom corners.
/sigh/ ok, fine, I just want to be able to full screen a window and still see what else is open.
Burn in hell and die.
I want to be able to easily switch left and right between open windows.
Go full screen or I will shoot you.
I want to move an open window into the other monitor.
You can't because you're full screen dumbass.
I want to let a window present a popup like they normally do.
You can't because youre full screen dumbass. Why would you be full screen?
I want an application like Slack to be able to popup and remove notifications when is appropriate.
Choose to have every single notification persists on screen until you manually remove it, or miss all your notifications.
Can't we trouble you for something in between, where we trust an application and let it manage them in a way that makes sense based on their context?
You can trouble me for something in between these cheeks, shit stain.
Like honestly, I fucking hate what an advertising and AI filled mess Windows is, but it can actually manage your windows and virtual desktops in a way that makes a modicum of sense.
It feels like a single Apple product manager decided that the way that they use their computer (a single application at a time, no windows to manage) is the only way anyone does, so who cares if we implement a nonsensical full screen paradigm, it makes one tiny niche edge case slightly simpler.
A) on windows that does not have to happen, that is a choice by the office developers. If they want they can instead close a window but still have a service running in the system tray that can bring them back up instantly. Famously stuff like Steam and Discord work like this ootb.
B) the alternative, is that on MacOS you either:
close the last window, and accidentally leave an application running that chewing up memory for no reason
think you're on the last window and go to explicitly close the application using Command Q, only to find out you still had another window open behind it or on another monitor that you needed, because MacOS provides no logical way of finding windows.
Mac OS has memory compression and paging built in. If you leave an application running with no open windows, it’ll be idle in that state (it can also be idle with open windows, if you’re not interacting with them or running calculations in them) and when memory is low the operating system will first compress the memory of idle applications and later page them out (copied to storage and removed from memory) to disk (a fast SSD on a modern machine). An application that is paged out is so fast to page in and resume working that I’ve never even been able to tell when it happens. It basically feels like the computer has infinite memory available.
In practice that means you can leave every single one of your applications open and you won’t have any memory issues unless they’re all actively working and allocating memory to get work done. I leave almost all my commonly used applications open for months at a time with no issues. If there were any applications leaking memory or wasting battery then the system would warn me under the battery menu (listed as an app using significant energy).
The Mac has tons of ways to find windows. For one, every application has a Window menu in the menu bar that lists all open windows, lets you switch to the ones you want (they may be on separate spaces) as well as more advanced stuff such moving and arranging and resizing all windows for an application:
Other ways to find windows include command-tab which cycles applications (but will bring up a window from that application if there are any open) and the trackpad gestures 3 finger swipe up to show all open windows in the current space (and be able to switch spaces or rearrange windows into different spaces) as well 3 finger swipe down which does the same thing but only for the windows opened by the current application.