The answer is the same as when this always comes up: mentally append "for realsies". The advice is meant to suggest that people not publish code or run services with incompetent crypto.

Nobody is saying not to learn and play. They're saying don't set off a rocket while staring down the engine. The reason why it has to be said is that the consequences of doing so when writing crypto are not so impressively immediate or dramatic, but just as devastating to the outcome (and maybe cryptographer, depending on adversary).

> Straight out of the CIA handbook is how you look when you repeat this bullshit ad nauseum.

The CIA does not care if you play with libsodium.