If you believe that "don't roll your own crypto" is some kind of absurd mantra the security industry uses to keep us in business, I recommend that you roll your own crypto, and keep us in business.
"Anyone, from the most clueless amateur to the best cryptographer, can create an algorithm that he himself can't break."
https://www.schneier.com/blog/archives/2011/04/schneiers_law...
I had found a similar thing making my own puzzles, "It's easy to make a puzzle you can't solve, but it's hard to make a puzzle that's fun."
Well, that' not entirely the same thing, but they overlap I guess.
I think it's worth drawing a distinction between the algos/maths and attempts at implementations. Otherwise we wouldn't have things like OCaml-TLS and others.