Can a non-functioning water softener cause any damage?

Question

It is a GE pro elite. It has not had any power for a few years but was still connected to the water main coming into the house.

Answer 1

No effect will occur. Water softeners don't reduce water pressure either.

Answer 2

All it would do is cause less water pressure at the tap.  So your shower would work better if the broken water softener was removed.