Anyone with $40 USD can buy a used 10gb ethernet card and wire it with cat6.
I don't know why you think there is some 'limit of thermodynamics' or that someone needs to 'invent new physics'.
Every computer for 15 years has come with a 1gb ethernet port.
2.5gb usb ethernet dongles are $30 USD and can be hooked into a $35 rasberry pi. A 2.5gb switch is around $120.
I don't know where you got these ideas, but they wouldn't have made sense two decades ago, let alone today.