Engine turning automatically off isn't the worst to be honest.
It could still be a part of the game, but i just find it a bit unrealistic to be a part of every vehicle in the game.

But i do think it could be removed completely, or changed:

1) Modders could have the ability to choose whether or not their mod would turn the engine off automatically or not.

2) Strictly only allow electric cars to use 'turn off engine automatically'

+1 on removal in its entirety

Engine should stay on until the user manually turns it off