One problem with this is that most people are typing passwords on phones now, so the longer they are, they more annoying they are to type in. (Although I suppose word completion would help with a passphrase. Although for security it probably shouldn't be enabled for password fields.) Anyway, the real solution is a password manager with unique random sequences of characters for passwords.

Perhaps Microsoft, Apple, and Google could get together to build (or buy and open source) a password manager that would be integrated with their various platforms, for the common good. (I realize solutions already exist, but this would make it much more likely that the general public would use it.)