Yes, it’s impossible
FBI Director Christopher Wray still fails to understand that encryption is a practice, like writing in Spanish, and not a proprietary technology. Even if all the companies that make phones agree not to distribute phones with strong encryption, that would just increase the space for third-party apps to provide that for voice and messaging and local storage. Many likely open source. Any law that would prohibit that runs smack up against the 1st amendment. Perhaps Wray is just looking for some compromise that makes things easier for law enforcement at the margins, for criminals too dumb or lazy to do anything other than use what is built into the phone. For the main, though, law enforcement just has to learn to live with encryption.