You can literally just look at Matrix, the tool you recommended, to see the problem with federation, fragmentation, and market demands to support lowest-common-denominator security. It took years after your recommendation for Matrix to have universal default E2E, the table-stakes feature of a secure messenger.
In fact, it is an argument that you were wrong, and the evidence for that is that when you made the argument, and for two whole years afterwards, your recommendation would have put vulnerable users on a platform that was for many users default-plaintext.
