And if we're arguing semantics, there is a tendency for conservatives to label "things done differently than before" as "political" and the status quo as the sane default, which it rarely is to anyone not in line with their ideology. Everything in civic life is political, especially in a democracy as ragged and divided as ours. The more precise question, I think, is not whether some person or institution is "political" (they are, unavoidably, especially if they don't even see their own politics) but whether they are responsive to democratic whims. The Supreme Court by design is way less so, vs the House say. And I'd argue that's a huge part of their problem. Society and needs didn't evolve as quickly when that institution was designed. It simply cannot keep up. 9 old farts who don't understand technology have no place governing the future of 300 million.
Lifetime appointments just mean they get to force THEIR politics on the rest of us, instead of being accountable to ours. It doesn't make them magically apolitical. They are partisan hacks appointed by shitty legislators elected by an antiquated electoral system participated in by a disenchanted and uneducated mass. The Supreme Court doesn't have a great track record of being some sort of enlightened wise guru above the fray, they're very much a part of the broken model of American representative democracy and its inability to cope with the issues of modernity.