I'm sorry, but whenever I go see either Fantasmic or the Fireworks show at the Disneyland Resort, they send out a cast member to make everyone stand up before they start. I understand Illuminations, as the time I went to see it I sat down and ate dinner, but in my experience at Disneyland someone always comes around to tell you to stand up. Everyone groans, but people stand up anyways.
From what I gather, the reason behind shutting down half of the park is to keep it dark enough for the projections to work, just like how they dim the lights for the fireworks show and fantasmic. I think people will have less of a problem with the policy of shutting down the rides once Cars Land opens, and have another place to wander to during the show.