"roll your own" is universally one of the worst pieces of advice in the encryption space. If you don't believe me, ask anyone familiar with that space or just look at history.

I'm all for one-time pads, but you're still having to secure the "password" or the key you used. If my password manager was every compromised, then I'd be screwed anyway. Files that don't need to be stored in a password manager because they aren't super important secrets can be encrypted and stored just fine on a blockchain. Again, in this case, there was nothing super secret about the data, other than putting it out there in plaintext would be kind of silly (and meaningless to others).

Rolling your own encryption is most likely going to be less secure than using established crypto. The chances of a security expert getting crypto right when designing a new algorithm are pretty slim. Yes, the key to decrypt the data might get found, but the likelihood of that, compared to a developer not being as smart as they think they are is not a tradeoff anyone should take.