Hey, Scott:
On this one, I somewhat blame Apple more than I do WGT. And, as an aside, I'm big Apple fan. Been using a Mac since about 2012 when I switched over from Windows-based computers (after over 15 years using Windows).
I think Apple is a bit too quick (at times) to obsolete older hardware. When they obsolete a unit, the user can no longer update the OS. On the other hand, if someone is running High Sierra and can't upgrade, that means their computer has to be at least 10 years old. When a new OS comes out (about one a year, IIRC), users can upgrade for free.
But as I mentioned in another thread, this situation isn't all that unusual. For example, a MacBook running High Sierra wouldn't be able to install the most current version of Microsoft Office. I tried. I have a MacBook Pro (early 2011) running High Sierra. Can't install Office on it.
And a couple of years ago, we had to get a new MacBook Air for my wife because the newest version of Quicken wouldn't run on it due to the age of the OS. And I couldn't update the OS because Apple obsoleted it.
By the way, High Sierra came out in 2017. What that means is since then (including Sonoma) there have been 6 updates of the OS.