I think you’re correct about some of the machines such as the 328p (Arduino) machines. Most of these have a clock rate of 16mHz, some can run at 20mHz. Along with, it’s a quarter of a century old..
They refer to these as a Cross Over CPU, as it implements, in this case, I think it’s a core 7 ARM processor, came into existence in 2019… Can’t really compare a 600mHz controller that’s 6 years old to a 16mHz, 8 bit quarter century old chip.
From that angle I think you’re right.
What a usb connection requires is a driver to interpret what the pair of usb wires are saying. With Ethernet, it’s required driver is built into your computer and there is no drivers to find and install. If you can connect to your lan, or wan, it’s working.
Ethernet is also pretty clearly backwards compatible. You can see where these usb issues are causing Mac users to put something in between the computer and device to force the Mac into a usb 2.0 configuration. One of the benefits that Mac has brought along with that of being state of the art.. 
Ethernet was commercially introduced around 1980, so it’s much smarter and better now that it was. USB came about in the mid 90’s. I don’t know when usb became commercially viable… Sure took off when it did.
The technical workings of usb are great, however personally, I’ve had them wiggle out and/or poorly created connectors… One of the issues with my fiber.
Of course the connectors used by Ethernet have locking connectors, so that’s not going to happen.
There are a lot of reasons I like Ethernet over usb. A lot of it has to do with how dependable Ethernet is compared to usb.
My Ruida uses UDP which is kind of sloppy.. and has no error control.
Maybe it’s just a comfort zone.
