The SC isn't supposed to concern itself with justice, that's a sticky matter for the legislators. Their job is to make sure that the legislators followed rules (wrote laws which do not contradict the constitution) and that those laws are properly applied.

Yes, every individual judge has their own skills and opinions and as such, sees the legal question slightly differently, and has different legal interests and thus knows some law more than other. We have a nine as a balance between not having enough diverse backgrounds such that we might be missing the critical input some day weighed against the group being to big to be convenient.

> why do we end up with split votes that so often fall down partisan lines?

People are flawed. Let's say some injustice caused you to get into law. You're likely going to be more familiar with that area, and more sensitive to its harms, than another judge. You may not be voting your ideology, you may be there (as a justice) because of your ideology, and you may have your honest beliefs because of your unique experiences.

I often read opinions I don't agree with, but I can see where the justice just had a different life than me and sees things differently.

> Supreme Court opinions literally called opinions, if they are apparently objective?

The only use of objectivity in this thread is yours. But if someone did use that phrasing, they'd mean that the justices should decide the same on the same issue, no matter if it helps a nazi or a nun. Justice is supposed to be blind.