It is shocking to me how many people in the computer community explicitly tell curious minds not to even try building a crypto protocol.

It isn't enough to say "you'll never get it right for production, please use a framework or library for production". You simply don't want them to even experiment on their own.

I agree with saying "the most effective way to learn cryptography is through books and tools X, Y, Z". But one would imagine that writing a poor hashing algo would open up a door to alternate dimensions by how superstitious some are about it on this site.