Scoring 100% on your ATPL's only proves that you can sit an exam.
In my view, you learn decision making in sh!t conditions only in the real world, when you end up in a situation where you wish you weren't and now have to get yourself out off it.
I dont have sim experience tough, but it would be in the back off my mind I won't get killed if I did stuff it up.
I can only imagen the pressure some poor sod would be under IF your grand dad in the LHS sniff's it and you are on your own in bad wx with a difficult aproach etc....
were as someone with a lot off GA back ground would think, I have been here before..... nothing to worry about, apart from could I start logging this as PIC?? lol
cheers