I’m not entirely clear on what you’re saying. It sounds like you don’t have a Hub (no Apple TV, no HomePod?)
You don’t need the very latest Apple TV to use as a Hub or to be on the new home architecture upgrade.
Upgrade to the new Home architecture - Apple Support
A HomePod Mini would be the cheapest option if you wanted to buy a Hub.
Set up your HomePod, HomePod mini, Apple TV, or iPad as a home hub - Apple Support - disregard iPad, as mentioned it can no longer be a hub once the architecture upgrade has been done.
I don’t know the answer as to why Apple decides which devices can be Hubs. Try not to confuse Hubs with the Home App. For example , the iPad, Mac, Apple Watch and an iPhone can still use the Home App but they can’t be “hubs”. And again this upgrade is not a software update as in iOS, tvOS or MacOS. It’s a separate, optional upgrade performed in the Home App that affects every device. Devices not able to update to the latest software lose being able to use the Home App. once the architecture upgrade has been done.
Your Mac needs to be running on MacOS Ventura
macOS Ventura is compatible with these computers - Apple Support
It’s hard to explain!