Photocopying books for example is in fact not legal. Same goes for redistribution of art u stole.

When it comes to fan art of Disney characters, the legal position is "Disney could sue you for that, but chooses not to as suing fans would be bad PR, don't do anything commercial with it though or they'll sue you for sure"

So - yes, as I understand things it can indeed be illegal even if a human does the learning.

If you copy an artists style with extreme precision without their consent, yes.