On my local network I want governance over my devices. I want specific firewall rules per device, so I can, for instance, block YouTube only on the kids devices. I want this to be centrally managed, so configured on my opnsense router. I want all devices to use IP6. Unfortunately none of this is possible.
To setup firewall rules I need DHCPv6, not SLAAC so my IPs on my local network that I manage are well known and fixed. Android devices don’t support DHCPv6. And the designers of IP6 were daft enough to set the priority of IPv4 above that of their new protocol. So basically if you have any IPv4 addresses on a device, they’ll be preferred by basically all operating systems - because that’s what the spec says. So you can’t run dual stack in a meaningful way.
TL;DR: IPv6 on a local network has not been thought through at all even though it’s incredibly old, it’s really immature.
Another thing that makes no sense is if my ISP provided prefix changes -which it will- this affects the IP addressing on my local network. Ain’t noboby got time for that if you’re managing a company or having anything other than a flat home network with every device equal.
IPv6 is just people shouting NAT BAD, but frankly having separate address ranges inside and outside a house is a feature. A really really useful feature. Having every device have a public IP6 address I’d an anti-featute.