ipv6 no doubt was designed without the mistakes that ipv4 learned the hard way. Everything from getting rid of useless (and dangerous) flags, to flow identification, is beautifully designed.

But, there is absolutely 0 reason for Google, Facebook, etc to know how many devices are operating in your home, or which ones they are communicating with. And before the army of drones screams "ipv6 privacy extensions", the battle has already been lost. Unless every request to Google, Facebook, etc was made with a unique ipv6 address, you cannot assume the same level of privacy that an ipv4 NAT provides. Ipv4 makes Google, Faceebook jump through extraordinary hoops to track you and monetize your personal and private life. Ipv6 makes these things trivial (coincidently, both of those companies are pushing ipv6 the hardest despite owning huge swaths of ipv4 space).