The only person who can try to pass such a pessimistic statement is the one who has not really tried themselves to get back together with an ex. These are the people who either plan on simply dating away their lives or do not want to let go of the single group of friends around them. They will feed you all these stories of how trying to get back together with an ex does not work in most cases. You have to concentrate on your work and avoid such negative inputs which try to demoralize you even before you have started. Listen to the right people and give it a try as only then you will be truly able to gauge whether your relationship was just waiting for a nudge to blossom.