If the front door is really locked by a tech implementation that actually works, then yes.
But internet makes things scale in a hardly to imagine way, and a "mostly locked door" easily become equivalent to an open door.
Imagine exchanging offline paper messages using some sort of Ceaser Cypher to crypt them. In most cases, if you are not an high target or someone is motivated to see the messages, you have a mostly closed door that can work for some situations, protecting messages from accidentally leaks.
Put that exchange-scheme on internet and you have an open door, you can consider your flawed encryption as exchanging cleartext. 

 this is why rule number one is: don't put sensitive data on a public network. period. 

 anyone who is trying to sell you any idea that you can ignore that rule should not be trusted and probably is a spook trying to keep the newbies confused about security 

 Mleku, this sort of wild accusation is where you lose your listener.