"With no disrespect to the developers at Apple, et. al., each one of these problems that goes viral before reaching "proper" channels..."
s/that goes viral before reaching \"proper\" channels//
The fact that the problems existed to begin with is more troubling than whether they became known outside the company or not. IMO.
With an open source UNIX-like OS (like the ones Apple sourced from for parts of macOS), both the developers and the users can watch the commits as they happen. Developers and users anywhere can choose to watch the commits and may be able to detect a series of poor quality ones. At least they can make informed decisions on the relative merits of changes from one version to the next. (Edit: They might choose not to compile or install certain components. I do not use X11. Nor do I use systemd.)
The fact that development of macOS is hidden from those outside Apple and that problems are protected from "going viral" does not make the problems any less of an issue for macOS users.
The issue is not how fast and secretively they fix problems, it is how many problems their developers are introducing into the existing version to begin with.
If there are problems routinely being introduced then no amount of fixing after the fact and behind the scenes is going to make the OS higher quality. Only due care taken before introducing changes will guard against further deterioration of quality level.
(Edit: The mention of open source is not intended to be interpreted as an argument that open source inherently results in better software. Perhaps skill and attention to detail are at cause. This is a debate worth avoiding.
The relevance of the mention of open source is intended to suggest that detecting and avoiding problematic software may be easier for some users, e.g. yours truly, if they can access the source code. As opposed to hoping that Acme Hardware and Software Corporation will quickly and secretly fix all software problems that slipped through their QC procedures. Too late for the user who has already paid for the software and updated to the new version. That argument should not be too controversial.)