Unbalanced ADC Match UPs

So I play as a Marksman and understand that each kit is designed around a central idea of how it should work but when you we really look at it, why does Vayne (The strongest hyper carry ADC) have a invisibility with her ult, a true damage with out cool down per target and then a knock back to stun. Now this wouldnt be so bad except they are making other ADC's obsolete such as kalista who just cause she can leap a small distance every basic attack, is not able to cancel auto attacks, loses 10% of her total damage and autos wont land if they are out of vision. So basically i wanna know where is the balance here, I really don't see it since if vayne gets a bork no matter what you will lose.

Vayne needs to be truly balanced.

May we have a Red explain what is going on to let some thing like this go unchecked for a whole season almost