1. Not all crypto currencies are public. See monero, haven, secret network. Although that last one depends on some specific features of some Intel processors... I'm of the opinion that the pseudonymous nature of public blockchains is very beneficial to society. I would love it if I could see what companies, governments, and people near me were spending their money on. It would enable me to make better decisions.
2. "Web3" is about decentralization but it doesn't necessarily mean storing data on a blockchain. The most important aspect is that users no longer have to sign up or log in. They submit responses which are signed by a key pair, which is their identity instead of a record in a "users" table.