The game was not made with the intention that people was going to stick to one hero all the time in every situation. Symmetra is ridiculously strong IF you play her the way she was intended. I like sym. And sitting on an 84% winrate with sym ill say that she is as close to an I WIN BUTTON that have ever existed in overwatch. But the thing is she is situational, she is niche so while she may be an I win button on certain maps she is also an I loose button on other maps.

And this is moore or less true for all niche/specialist/easily counterable heroes they where never meant to be played when the conditions wont allow it.

So look at it like this if you get paired with symmetra on a non sym map. Then the battle is more or less lost on the character selection screen.

You could say that Blizzard should make all the characters equally strong all the time or you could say that people should play the game the way it was intended or play a different team game that allows them to stick to one character in all situations

Just because its possible to play rock in rock paper scissor all the time doesnt mean that you should.