Question about the mourner’s kaddish

So I was saying kaddish for a long passed grandparent the other day and a question arose from a family member after reading the translation. It’s a prayer for the departed but like, it’s all about Hashem and how great He is plus a little bit about the living? I know we’re not so big on the afterlife but after it was brought up to me it struck me as odd too. Why is that? Is there any other payer that’s more about a passed loved one?