so you are saying it doesn't matter how skilled a Symm is they would never be able to take on an equally skilled Tracer? Really? I highly doubt this.
But what does Symmetra do if Tracer stays out of range? Even if you're at low health and try to hide in your room of turrets, she can still kill you and recall that health. And if you're forced to stay in your room of turrets to stay safe, then you're not in the fight and Tracer is countering you. Not to mention that Tracer bomb kills your teleporter/shield generator as well. I'd definitely say Tracer is a good counter for Symmetra in general.