About not using your crypto until it's been vetted by professionals… How do you get those vaunted professionals to even look at your work? For instance, I've been working on Monocypher for over 3 years, and the only way I could get professionals to actually look at it was to pay $7.000 (out of the OTF's pocket, I don't have the money). That's an unrealistic bar to meet, people need other ways to vet their work.
About CTF (Capture The Flag), and cryptopal challenges, my advice is: don't waste your time. The penetration testing approach to secure systems does not work. You whack a mole, two more appear. We need ways to prevent whole classes of errors, like proofs. For instance, tools like https://verifpal.com/ can be a great help when designing a protocol.
On crypto being deep and vast, it really depends what you're doing. While perhaps less than 50 people in the world are truly qualified to design a new cipher, that's not what people need when they "roll their own crypto". Most of the time they need a new implementation for an existing primitive (embedded programmers), or they need to invent a new protocol. Either is actually accessible to any professional programmer who actually follow the rules.
Even side effect circumvention. programming without the "if" statement is not that hard, especially if you stick to constant-time friendly primitives.