The trouble is that there's already a significant amount of precedent here holding that the Constitution doesn't treat this kind of information passing through

The trouble is that there's already a significant amount of precedent here holding that the Constitution doesn't treat this kind of information passing through intermediaries the same as letters through the mail. Congress had to pass the Stored Communications Act to provide any sort of halfway-reasonable protections for email stored on third-party servers, for example. And it can be pretty un-reasonable itself. Encryption changes things substantially, at least for practical purposes, but the whole idea of EARN IT is to coerce services to disincentivize the kind of encryption that would matter. The Court has made some baby steps in the direction of fixing the more "core" deficiencies of the 4th Amendment's protections given the realities of the modern world, but they're not showing any signs of rushing to go further.