Why does the latest home architecture update force other users to upgrade?

I just got the Home app notification to upgrade my "home architecture" after getting two HomePod mini's, both on iOS 16.5, there was a warning stating that other home users will not have access until they update their home architecture. Thinking "oh, cool so this should just be the same thing, they just open the Home app and presto hit 'Upgrade'", nope, just a message saying 'Unable to view home' with a link to 'Learn More'.

Have we not considered those who have an iPhone X or lower? People in my home are now fully kicked out of my home app now, even though their phones are perfectly fine. The warning "before you upgrade, other users will need to upgrade their home network" doesn't adequately state "if they cannot update to iOS 17 for whatever reason they are screwed".

This is a recipe for forced obsoletion, I see very little reasons for no backwards compatibility. For example, if I can airplay stream from my Windows PC using iTunes, after upgrading the software independently there, so I should be able to do this on my iPhone/iPad/Mac. What's the point of the App Store otherwise?

Also, immediately since upgrading the home architecture, my whole home internet crawls to a halt, crashing my modem when using Airplay streaming to the HomePods. This 'upgrade' has in-fact been a monstrous downgrade.