During Instrument flying traning pilots are trained to manoeuvre the aircraft accurately purely according to the instrument indications. When a GA requires 15° pitch up but is executed at 4 or degrees isn't it poor flying? I will again say that it all starts with giving pitch inputs without looking at the attitude indicator.
I suspect you have never experienced SI.
Training and awareness is key to survival in my opinion. When I have experienced it the problem is not one of poor instrument flying skills, nor lack of scan. It is a problem of perceived conflicting information.
The sense that you are pitching nose high, almost to vertical, is so strong that the other sensed cue ( visual) of an AH at 15 degrees nose up is difficult to believe. The conflicting sensed information takes some processing and a decision has to be made to ignore the seat of the pants and go against every fibre in your body and maintain the AH pitch required. The second time you make this decision is much much easier than the first. Solid training and awareness of the illusion is key to being able to make the correct decision. A brief twenty minutes prior ( not that I’ve ever done this) would be hugely beneficial in avoiding the hazards of SI.