@Adam 52
No, the original statement is absolutely true. Your assertion that we've done it with paper and comms is a false one. In those cases as with this, the bad guys could employ most of the same tactics to snoop that the good guys used, it was just illegal for them to use them (which is a fairly low bar when you're a bad guy).
The current situation is further complicated by the fact that monitoring, whether good or bad, happens in an unmonitored location, so it's hard to know exactly who is monitoring until they take some action.
Add the fact that the "terrorists" will simply start employing e2e encryption of their own or other methods which require no encryption at all and you really haven't accomplished much towards your stated goal. Bear in mind that drug dealers have managed to avoid capture for decades in a world with no encryption despite being high value targets.