It’s an old discussion—goes back to antiquity (e.g., Seneca), and Bacon, and many others. There is a fairly common view that death itself can’t be bad, but dying is often quite bad. The ethical upshot of that is pretty obvious: making dying less bad is good. There are other arguments for the badness of death, in e.g., Parfit’s Reasons and Persons.

Here’s an article that denies that we can measure the badness of death for the person who dies: https://doi.org/10.1017/S135824612100031X