This is yet more evidence that Apple's software engineering processes are broken. The release cycle is nonsense and results in unfinished features and products shipping with serious delays or not shipping at all.
I never thought I would say this, but Microsoft's release cadence is now making a lot more sense than Apple's. In the old days, it was torturous waiting months or even years for Microsoft to ship service packs to fix problems, but with Microsoft's current practice of releasing fixes every month and then releasing significant updates twice every year on a regular schedule—without releasing an entirely new OS, thus preserving stability—they are putting Apple to shame. Windows 10 is a very stable and predictable product at this point.
macOS is not a stable product—especially at release time. Apple needs to stop throwing stuff out the door and rethink how they approach their release and development schedules. They are embarrassing themselves and making life a lot harder for their customers.
While I agree with you that annual releases are not currently sustainable at Apple, it is not the reason for all of this issues they're having. After all, we saw with iOS 12 that if they simply focus on optimization and bug fix, they can release a solid update within a year; same with the macOS release that time, I think it was Catalina or Big Sur.
First, Apple is not releasing a new OS every year or even every 5 years, no one can rewrite an OS every year, it takes decades to do what current desktop OS can do, they're one of the most complicated codebases on the planet.
macOS 12.1 is the same OS since Snow Leopard or some might say Lion but the reason Apple did SL was because they've reworked the core with the plans for that release to be ready for the _next decade_ of releases.
Apple needs to do another refactoring of their platforms but I think they're likely waiting for Swift, Mac Catalyst, SwiftUI to be more mature and other tech like the Apple Silicon transition to be done before they do that (end of 2022). So, give another year for things to settle down, I suspect we won't see any serious reworking to even show up until `2024-2025 (they'll remove Intel stuff as well).
As for Windows 10, remember that Apple has multiple OSes they're working on at the same time to ensure vertical integration support is solid; watchOS, iOS, iPadOS, macOS, tvOS and so on. Microsoft doesn't have features like universal clipboard sync, side car, etc nor do they build a mobile OS and so on.
Also, Windows 10 isn't that stable, I had bad upgrades 2-3 times from Windows 10 in the last two years alone. If Windows 10 is so stable, they wouldn't be releasing massive long of bug fixes every single month.