And I have a pretty strong feeling that you are a Mac fanboi, jumping to a conclusion despite hints against it, simply because someone criticised your religi^H^H^H operating system of choice. ;-)
1. Oh yes, Mac has the easiest installation process. Deinstallation, not so much -- yes, you can draw your app to trashcan, but that leaves bunch of data files, configurations (depending on the app) etc on the disk. That is the reason for existence of a number of uninstallation utilities like AppCleaner or AppDelete (my tool of choice). And while Sparkle is useful, it is a third-party effort and not aprt of the OS.
2. Oh yes, brew is simple, there is no doubt about that. Except when a package becomes corrupted (e.g. while upgrading, or when there are missing dependencies, or when you accidentally install the same thing in two different ways), in which case it becomes a nightmare to untangle.
3. Oh yes, the gatekeeper is very useful -- unless you disagree with it about what represents "trash". And honestly, my strong belief is that Apple is going to restrict the other ways to install apps in favour of the Apple Store, moving towards a "desktop iOS"; which is perfectly fine if you just want to use certain apps, but isn't if you're a software developer building anything other than MacOS or iOS apps.
Edit: Just to clarify, I am giving my own opinion and pain points which have been turning me away from the Mac for quite a long time (and it's only getting worse). It is not my intention to force my opinion to anyone else or to pronounce Mac the worst and Linux (or anything else) the best choice. It's simply the case that each OS has it's own realities, and some are better fit for some purposes, and others for others.