In nature and in life there is a life expectancy. A flower can grow for so long until it dies, Some plants will only grow food once before they die. Not all plants can sustain life and continue to grow food season after season. This is the same with humans. Your body was made to last for a certain amount of time. As the years pass your body takes on a great deal of strain. For a while, it can handle this because you are younger and stronger. But as you age your body's muscles and organs start to deteriorate and get weak. When this happens the body starts to fail in health. There is nothing that people can do to bring back youth and make a person live forever.
Anyhow the plant that we live on wasn't made to accommodate so many people. Right now it is hard for some countries to even grow enough food to feed the current population. If you added this population and all the generates that have already passed on, the earth as we know it couldn't feed everyone and there would be too many people staving.
It is hard to let go and say goodbye, but we all have to do it. This is how the world was built, from plant life, animal life to human life. There are a cycle and a time for living and one for dying to make room for the next generation to take our place.