I disagree, because it could be prevented by not training on copyrighted material in the first place. You can't reproduce a highly-unique Nat Geo cover photo if it hasn't been encoded into the model. You can't reproduce watermarks that aren't in the training set. Remember: it's an algorithm, not person. The outputs are directly related to what's been encoded into the model.
> The act of training a model hasn't currently been judged to be illegal
It's outside of the rights granted by the copyright holders in most cases (MIT and CC are probably the few licenses which allows this, and even CC/NC wouldn't allow it and MIT falls afoul of the attribution clause).
The legal system hasn't yet reviewed such widespread infringement yet to create precedent. But eventually it will, and I don't believe it will be kind.