Have you ever worked with folk who can't make a decision? They faff about "maybe this, maybe that", they can't prioritise, can't see the big picture, get overwhelmed by the detail? Can't see what MUST BE DONE RIGHT NOW and what can wait?
I always think these folk should go learn to fly a small aerobatic taildragger out of a farm strip. Nothing else sharpens the mind like being solely responsible for preparation, field state, go/no-go and wx decisions, W&B, fuelling, fitness for flight decisons (you and the aeroplane), and the myriad other stuff you have to deal with in real time as sole operator, especially if it starts to go pear shaped.
To me it's inconceivable that anyone who hasn't done all that, and quite a lot of it, should go anywhere near an airliner flight deck - either seat!