Yeah you're right, the 'crypto guys' would've probably just said "Don't even try it because you'll kill people and even we wouldn't want to try and do it".
Crypto is hard to get right, that doesn't mean anyone shouldn't even bother trying.
Crypto is hard to get right, that doesn't mean anyone shouldn't even bother trying.
Likewise, building a hot new secure messaging app with existing well-analyzed, battle-tested cryptographic schemes is generally going to be welcomed.
If you try to do both at once, you're building your application on shaky, untested cryptographical foundations. Cryptographers would similarly probably warn you not to base your application on a new cipher someone else announced at a cryptography conference last week - give it a bit of time for others to analyze it and spot any flaws it might have before you entrust anything sensitive to it.
I could go and try to play around with real time systems for flying planes, it still wouldn't make sense for me to sell you the "safest" plane in the world without going through the proper steps to get such system certified beforehand.