Personally I'd separate this out into two cases:

1 - Actively dislike the family

Sure, skip the funeral. If you & the family didn't get along in life there's no reason to put yourself through something you don't want to go to.

2 - Anything else

I'd go as a show of support for the family because the family was important to my friend. "It's what my friend would want" is the guiding principle here.

That said - I'm writing this as someone who was very uncomfortable going to funerals and now, years later, I regret choosing to stay home rather than go.

Your mileage may vary, as they say.