Which part do you think it’s FUD, and why?

PGP is not particularly related to email. It’s also used to encrypt files, partitions etc.

You can use public key cryptography with any system, because you simply encrypt the content and then send it through the normal unencrypted system.

But PGP does nothing for the headers and nothing for the fact messages are still waiting around on various servers. Also PGP on its own is very impractical due to the need to get keys for every recipient – but even if there were a generalized system of public key autodiscovery (over DNS) it still wouldn’t fix the problems with IMAP/POP3/SMTP.

Each of these things holds a piece of the puzzle – including what Proton & Tuta are doing – but these pieces on their own are useless. We need all of them to come together.