> But we'd still end up with server-client cloud architectures, even if we had started with IPv6 in the beginning.

Skype was originally peer-to-peer for comms, but ended up with "super-nodes" because of NAT limitations (not sure if STUN/TURN/ICE had been invented by that point). BitTorrent is still peer-to-peer. A number of folks ran Mincecraft servers at home, but you'd only be able to have one on the default port.

But this doesn't only hurt server-y stuff: you may not notice it if you're with a legacy MegaISP with lots of money to throw at IPv4 allocations, but if you're with a younger or smaller ISP, then there's a good chance you're behind CG-NAT, so many console games won't work.