Sorry for your losses.

Funerals are rituals that help the living accept and start moving on after someone has passed. If you don't need this then don't go.

That said, if this person's family are friends of yours then you need to go to support them. Being there shows respect for your friend and for his family.

When my Mom was dying of cancer she said that she thought she could count her friends on one hand. She was surprised how many people came to see her. She would have been truly surprised to have seen how many people showed up for her funeral. It was the largest funeral gathering that I have ever seen at her church, and I have been to quite a few funerals there. There wasn't an empty space in the pews.