It is easy to ban what are currently the most popular apps for encrypted messaging. But the math is more or less trivial, to the point that this will simply kick off a cat-and-mouse game the government cannot win. And that is before steganography comes into play.

At the absolute worst, OTPs are trivially uncrackable and relatively foolproof, assuming you can exchange keys out of band. Furthermore, it is trivial to generate keys that decode captured ciphertext into decoy cleartext, should the government try to coerce the keys from you.

I'm not saying OTP is practical for regular people in everyday chats (though it certainly can be for text, in my opinion). However, it is apparent to me that if RSA+AES becomes unviable, for example, then it will have nearly no impact on any criminal operation that cares about security.