I think it comes down to how both sides view impartiality. There's definitely confirmation bias when the president nominates a judge - often the candidates come from the same party so they share some broad ideological positions.

Most judges I think do see themselves as impartial jurists even if the results tend to skew toward political outcomes.

Hah! That’s not the “confirmation bias” I’m used to, but very apt.

Agree it seems a bit wrong. Worth bearing in mind that cases which go to higher courts are usually ones which lower courts think aren't clear, or different courts disagree.