Well, I'm inside a CGNAT. It's like living in an apartment building with 20,000 other families. Maybe it's all fine when everything is normal, but one day, the water pipe on the top floor might go burst while no one is answering the door.
It is true that a NAT could give you some privacy, but the downside is also very obvious. For example, your network neighbor might rub some service in the wrong way, then the service ended up sanction/ban the shared NAT exit.
Then, you might be thinking, "just use a smaller CGNAT then". Well, then a smaller CGNAT will allow the website to track you more easily.
If I really really don't want to be tracked, I'd rather use Tor.
In that analogy, the /64 is their specific apartment, not the whole building. That is, they wouldn't get banned for something their neighbor did, because their neighbor would be in a separate /64.
That is, the whole /64 is equivalent to the single IPv4 address they have in their home router, not to the CGNAT which combines several home routers into a single IPv4 address.
Ding ding ding. IPv6 doesn't solve this problem either because not all malicious activity from a given IP address is guaranteed to be conducted with the knowledge or consent of the folks paying for the connection anyway.
There should only ever be discrimination against traffic, not against addresses. Addresses should not be presumed to be fixed, and it should therefore never be assumed that seeing the same client IP twice means it's the same end user.
It is true that a NAT could give you some privacy, but the downside is also very obvious. For example, your network neighbor might rub some service in the wrong way, then the service ended up sanction/ban the shared NAT exit.
Then, you might be thinking, "just use a smaller CGNAT then". Well, then a smaller CGNAT will allow the website to track you more easily.
If I really really don't want to be tracked, I'd rather use Tor.