Pace
Exactly - maybe too much time spent on flying to tolerance and more needed spent on coping with situations - the trouble is the first is easy to test, the second much harder. Sim time goes a long way to achieve the second but doesnt work for most light aircraft.
Real world experience comes from doing, so I suspect your rating needs to get you to a point where you are essentially safe but realise you don't yet have the experience.
There is no perfect model, but I dont think there is any evidence that an IMCr combined with an EIR will create problems which seems to be the substance of this thread. After all I think we agree the en route part is the easier part and IMCr holders have been doing the other part for a long time without evidence of shortcomings.