But then you can combine stuff as I've for example written in another comment to roll your own crypto in five minutes, which is not-unsafer.
There is cult around "Don't roll your own crypto" that is thought-policing.
Furthermore, your argument is fallacious. That expert professionals make mistakes does not tell you anything about the likelihood of an amateur to make a mistake. You can't draw any logical conclusion from that statement on its own.
(btw, I do develop and deploy my own rockets for fun)
Even were that as accessible as developing and deploying your own cryptography, I'd still advise against it.
You know who else gets "thought policed"? The people who actually need to rely on cryptography. In their case it isn't grumpy people on Internet message boards telling them not to do something, it's agents of the state killing them or imprisoning them for many years.