Comment by compounding_it

NAT is just one slice of IPv4. Granted your private IP is not routable (with CGNAT now your gateway is also no longer routable), but think of other features of IPv6 that are congruent:

SLAAC basically means your routable IPv6 address changes so many times in a day (and there are multiple of those at any given instant) that even if the attackers know your prefix, its going to be very difficult to do anything meaningful. the address space is too big.

And we are assuming here that there is no firewall.

Note : macOS firewall on a new install is disabled iirc.