Usenet is client-server, not P2P. The issue with “good performance” on P2P systems is that you’re reliant on other users’ bandwidth, and there’s a lot of people in the world that have slow upload speeds. Some users use a seedbox with a fast datacenter-grade 10Gbps or 40Gbps connection, but it’s not common. The obvious approach if you want to download something from people with slow connections is to download parts of the same files from a lot of them in parallel, which is exactly what BitTorrent does. That’s good enough for plenty of use cases, which is why BitTorrent has been around for so long. It’s got plenty of legit use cases too, especially in research (where it’s common to have data files that are tens or hundreds of gigabytes and need to be shared with other researchers) and in gaming (where it was common to use BitTorrent to download updates, at least outside of Steam).