If the graphics look rubbish out brain will feel sick.

That is not what causes VR motion sickness.

It is the disconnect from the movement signals our brain is receiving from our eyes via VR and our vestibular organ which tells us our physical orientation.

VR motion sickness has the same cause as seasickness and car sickness and all testing I have seen is that about 1/3 of the population will never be able to use VR without getting sick.