The host side issues were pretty much all related to BSD Sockets being shittiest, but cheapest, network stack on the block. For many years it embedded the idea

The host side issues were pretty much all related to BSD Sockets being shittiest, but cheapest, network stack on the block. For many years it embedded the idea that every application had to handle exact details of each protocol it wanted to support through its exposure of gory details in sockaddr struct and requiring that as input to connect() and listen() calls. All the SLAAC, privacy address, etc? That's just an emanation of people cargo-culting some practices that were workable with IPv4 but only by making the network suck. And ifconfig got deprecated because it didn't fit linux networking API anymore, and nobody wanted to maintain it instead of writing something that fit well - which was iproute2.