Just don't. Please. Unless somebody has died or been seriously harmed.
We still have to respond to all complaints within a timescale. I stayed at work till a stupid time to get the complaint back last week - didn't mind that because a grieving family needs that closure.
However a big proportion of complaints at any one time are about how people feel about treatment or are about trivial issues that caused no harm. We don't have time for that right now.
We know the strengths or our weaknesses better than you. Please don't take time pointing them out right now.