I'm not entirely sure if CGN will provide some legal protection for pirates but it might make it harder to pirate content as you cannot open ports on CGN meaning BitTorrent will have less seeds which slows downloads. Afaik, IPv6 will make piracy extremely easy as UPnP won't be a requirement. Want to share a file with some friends? You can quickly spin up a web server, send them the URL and it'll just work.

You still need UPnP or something, otherwise your IPv6 default firewall policy (allow out deny in) is going to block inbound connections.

Yes, it's easier to hole punch, but a webserver won't do that.

And if you're manually configuring a firewall, I'm not sure "allow port 80 <someIPv6>" is any easier than "forward port 80 to <someipv4>.

What am I missing?

I think you are missing a lot. For instance, I have IPv6 set up at home, at work and at some homes of friends and family. I have firewall rules setup such that traffic from subnets I know is generally allowed instead of allowing access to a single port for the general internet. I also have DNS set up with names like computername.sitename.mydomain.tld

That allows me and the people I know to connect to each other's machines in a way that wouldn't be possible with IPv4 and NAT. I can be at my brothers and type \\[fqdn] in explorer and it will just work. To me, that is the way the internet was meant to function from the beginning.

If you're able to configure firewall rules, you're well outside of any normal users able to make up a significant amount of P2P traffic. And to most users, port forwarding and configuring a firewall rule are nearly identical.

Truth is that for most users, NAT today is almost always synonymous with a firewall that has deny in, allow out policy.

10+ years ago, a lot of folks often connected their machines to the Internet in the way you specified. You could go around scanning people's systems, viewing their fileshares and so on. NAT "fixed" a lot of that.

First off, good luck trying to implement any kind of decentralized network service when almost nobody has a globally routable address.

Second, if ISPs are willing to keep records of IP-address-to-customer mappings, it's not much of a stretch to add TCP/UDP ports to those records as well.

The IETF has (sadly) specced logging of cgn associations for surveillance purposes.