For Modern Standby to work properly, the device Windows is running on needs to support it. That includes hardware like network interfaces and USB, but also support from system firmware and device drivers.
But Microsoft doesn’t seem to have any sort of certification process or runtime hardware check for Modern Standby compatibility.
The important part, for the lazy:
Easy fix, it will be a requirement for Windows 12, unfortunately you all need to buy new computers ¯\_(ツ)_/¯