You might think that the law is antiquated, but this does not absolve anyone from complying with it. That cameras are not specifically mentioned in the exceptions means that passengers potentially leave themselves liable for prosecution if they use cameras during safety critical phases of flight.
Furthermore the "...nor may any operator or pilot-in-command of an aircraft allow the operation of..." means that the crew needs to ensure you (SLF) do not use any unauthorised electronic devices. If you fail to comply with their instructions you could also potentially be falling foul of the law, in New Zealand this is CAR 91.5 (Compliance with crew instructions and commands). Likewise, if the crew fail to ensure you are complying, then they are at risk of falling foul of the law.
I suppose another way of looking at it is driving along a straight road with no traffic above the speed limit. Even though it might be safe (in the sense of not having a crash, you perceive it as safe), you are still breaking the law, and if you are caught the police probably won't care that you were able to do so safely, they will just issue the ticket.