On the one hand in this thread there are posters, mainly passengers but a few CC saying in reality the evacuation procedures are flawed, and on the other there a few saying that its nothing to do with manufacturers or airlines, its the passengers who are a problem. Maybe you should find another set of passengers.
I wouldn't say the system is flawed, as such. That only happens those that make the rules stop listening to people like Jean and dismiss them out of hand as "stupid". It would be great if every single possible scenario or problem had been thought of prior to anything happening but the aircraft and the weather generally haven't read our SOP's. Nor have the passengers. And neither are exactly known for doing exactly what we expect them to do at all times.
With the demo, we have a very short time to get as much information across as we can and this is not, as suggested, to prevent delays on reaching the threshold! It's because the longer you babble on and on, the more people you lose as their attention starts to wander. That's why crew have to be trained to adapt quickly to changing circumstances and the SOP makers have to be willing to change or tweak procedures when someone ends up standing on the wing looking for a non existent slide.
Unfortunately, short of forcing people to watch 12 hours of Aircrash Investigation prior to every flight, no amount of safety procedures will remove the biggest danger to any successful evacuation. Complacency will always win.