Meanwhile I can still run software I wrote 40 years ago without even compiling it on Windows.
My team (including me) writes both host-based (Windows PC + Android) as well as embedded audio signal processing software (Tensilica HiFi 3/4/5 et al), with operating system-level audio integration, and I can assure you that very little of it "just runs", compared to higher-level application software from 10-15y ago. The Windows audio subsystem changes somewhat frequently, leveraging ever-more-efficient hardware designs to extend battery life far beyond that which would have been possible even 10y ago, though–ask any Windows driver engineer about the frequency by which HLK tests newly fail across subsequent versions of Windows.
This is the nature of tighter hardware, software and firmware integration; product designs change quickly to ensure better performance and, as many manufacturers have experienced, it's no longer a given that the underlying hardware or commodity components might remain unchanged (or available).
As for Apple, iOS and mobile handset product cycles in general tend to be driven (by mobile telephony carriers) as you've described, though this churn seems to slow down the larger and pricier the screens get (handset => tablet => laptop => desktop). Microsoft would LOVE to be in that business, yet they've failed to adapt to the mobile telephony market.
My decently-specified 2018 Dell laptop cannot run Windows 11, yet my 2014 Mac mini has no issues with the latest macOS. I think you have this backwards.
In the case of DAW plugins, the underlying applications also change frequently, even on "slower" platforms, which breaks compatibility (though, in the case of AUv3 and VST3, these changes are ultimately for the better). I don't see any blame being thrown at Steinberg; they control the VST specification and licensing, and not Apple. There are still developers complaining about having lost access to VST2 SDKs.
And, as for the Virus–ask yourself as to why Kemper's Rig Manager application continues to gain regular, cross-platform updates, yet the Virus VST plugins do not (HINT: it has nothing to do with Apple, or Microsoft for that matter).
Ultimately, this is the rationale for selecting products from manufacturers that will continue to support them as long as they can.