You need to remember the very real dangers of the evacuation process. Initiation by someone other than the flight crew is particularly dangerous because the aircraft is highly likely to be in a very unsafe configuration. Maybe consider imagining there is a pride of hungry lions outside the aircraft? Are you better to remain within the protection of the cabin, or are you better off taking your chances with the lions? If you think you are better off staying away from the lions, then you shouldn't be initiating an evacuation - you should be contacting the flight crew and telling them what you see as accurately as possible.