What are you saying, isn’t the opposite true, most of the Jews not alive today would have ended up existing?
That’s absolutely true. But I’m not convinced that it’s morally and ethically good to sacrifice the millions of people that currently exist for the millions of people that could have existed.
Were that the case, you could never make a marital decision in your life. Sure, marrying my wife helped my kids come into existence, but it also precluded the large number of alternate possible other children that might have existed had I married any one of the thousands* of other available women. But we have to make choices in the here and now and cannot be concerned about the unknowable possibility of lives that might come into existence if we took a different action.
The Wolf
* Not that there were thousands of women who would have wanted me, but you get the point.