Not sure where you're getting this from, but the latest MacOS works on devices from 2019 so it's at least 6 years of support. And homebrew supports versions from macOS 14 fully (and some support up to 10.15) which means full support for 2018 devices and potentially even devices from 2012 will work.

Sources:

https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

https://docs.brew.sh/Installation#2

Which device was only supported for three years? Even the final Intel Macs are getting six.