Not sure that it matters, but I noticed on my MBP the asix driver sets the speed to 100baseTX, the ASIX interface is supposed to be a gigabit interface?
I have the same exact experience hachiman. I just recieved my mk7 this week. I just went to set it up on my MBP with big sur and same experience. Plugged it into my dell XPS w/ windows10 and the usb-c works fine. I installed the driver in osx, I was checking tcpdump, same exact thing, it was requesting for an IP but never a response.