[1] https://www.supremecourt.gov/opinions/20pdf/18-956_d18f.pdf
The decision does show that the Supreme Court justices are savvy as to how the tech industry works, at least they know from a policy perspective they can't strike down the whole Android ecosystem without causing mayhem. And they know they can't affirm copyrights of APIs for similar reasons.
But from a legal perspective the way they outright dodged the legal question they were supposed to answer (i.e. are APIs copyrightable?) and the way they just asserted the conclusion about fair use without pretending to apply legal reasoning (together with a disclaimer that they haven't tried to change the existing law even if it looks like they have), I wouldn't say it's one of their better decisions.
As you say, in general people in tech have a tendency to assume judges are idiots. Most often they aren't, because judges sitting in the top courts are a handful of people at the pinnacle of their field, and they don't get there by being idiots. I agree with you that it's a good idea to sample some opinions from Supreme Courts or perhaps even others appeal courts to gain an appreciation of how judges tend to think. I just think Google v. Oracle is one of the worse ones to start with..