Maybe not a delete button, because then we might accidentally delete important moments.
Plus, we all learn from our mistakes. If life had a delete button, it would be abused. We would never learn from our mistakes, and it can cause chaos. Life lessons are important.
It is upsetting when something bad happens, but then we learn to never do that again. And when it comes to a persons death, it was just their time. Everyone has a time when their heart stops beating, and they go somewhere in the clouds. Death and life lessons are a natural cause. You just have to accept what had happened, and move on.