> but it's really easy to set up a network to have dual-stack v4 and v6

Why do you need v4? because v6 doesn't work.

> NAT or port forwarding, both of which are terrible

Why? I assume you're still using a stateful firewall, so what difference does it make.

Normal source-nat has many benefits too, for example when you want to send some traffic via ISP1 and some via ISP2, controlled at the network layer, and you aren't BGP peering with them.

> Meanwhile with v4 I have to port forward all web traffic to one server, then reverse proxy it to its final destination

Or just use two IPv4 addresses. Personally I reverse proxy my servers anyway to have a single (well dual) point of control on entry at an application layer, ipv4 or ipv6 doesn't matter.