It's interesting how long we've been waiting for fair queuing to fix congestion problems in the Internet. The first proper research on this was published in 1989:
https://dl.acm.org/doi/10.1145/75246.75248I'm a big fan of fair queuing, and have it enabled for my home network. But in core routers, the best approximation is likely to be WFQ, where you're likely to have each flow hashed to one of something like 256 queues. This means one badly behaved flow can't force well-behaved traffic out of the way and take over the whole link, but it can take over its WFQ queue, starving well behaved flows that hash to the same queue.
I'm not aware of any backbone router that implements true fair queuing. But even if all routers did, it's not a complete solution. Typically flows are mapped to queues based on the 5-tuple (src IP, dst IP, src port, dst port, proto). If you do this, then all Brutal-NG needs to do is use many source ports so it gets many queues, thus many times its fair share, and take over the link again. In fact, this would enable DoS attacks on router state, so no-one is going to do this.
An alternative would be to map to queues using just the source and destination IP addresses. But this has problems too. Brutal-NG could spoof the source address of most of the packets (but send ACKs back to the one unspoofed address), again taking over the link. And it could still cause DoS issues on router state.
The only thing you can't spoof if you want to actually exchange data (as opposed to DoSing the network) is the destination IP address. But now one Brutal flow can achieve the same fair share as all the traffic headed for a busy Google server or an entire ISP's CGNAT. Equally, one flow Brutal flow sending to a host behind the CGNAT can deny service to everyone else sending to the same CGNAT IP address.
So in the end, while I really like what fair queuing does for my VoIP latency on my home network, it is unlikely to ever be a complete solution for constraining misbehaving flows.