> So the ancient WPS printer in my garage is entirely unsupported without deploying a computer running Windows or macOS, installing Chrome, and registering a "classic printer"
I think the support text is wrong—you could do this on Linux as well. It'll be a moot point though when Cloud Print shuts down.
> Why is CUPS gimped so badly on ChromeOS?
Have you tried recently? I don't think it is anymore. Yesterday my Chromebook seemed to just see my printer on my local LAN (via Rendezvous, I assume).
I agree these product/support docs you linked are pretty alarming. But I think the actual situation is (or if not is, will be) much better for basic ChromeOS in simple situations:
* auto-discovered network-connected printer on the same LAN as the Chromebook
* network-connected printer where you know the hostname and it's reachable from the Chromebook
* USB printer connected directly to the Chromebook
Hopefully those docs will improve soon...
Note that while I work for Google, I don't have any inside knowledge of this.