I would argue that bandwidth-sharing fairness with stuff going over UDP is easy: Just start dropping packets when pipes get full.
Most updates are going to be pretty small. It's not like game developers want the user experience of their titles to be bad, after all.
You’re not consindering a server, the bandwidth is very high on the backend and does saturate links. You run many servers per physical or virtual machine due to cost, so you can have 1000s if players connected over a single network path.
At the datacenter level you're making sure that the bandwidth you bought from providers is sufficient (and ideally, redundant), and that you can shift load from one area to another if necessary. You can buy this capability from AWS or Azure, or build it yourself in many different ways.
In fairness that was probably a crucial component of the Internet's success, but you don't get the good w/o the bad.
But re: "this will result in bandwidth hogging", routers will just drop your packets if you oversaturate them, so that's not a worry in practice. Well, it is for developers but they use rate scaling algorithms in those cases.