The GP alluded to "a handful of terms everyone agrees are reasonable". Regardless of what those are, their hypothetical definition makes them implicitly reasonable. You can circularly reason that these hypothetical univerally-reasonable terms are univerally-reasonable because it is impossible to abuse them with a severe power imbalance.

Re-reading your post, you appear to be asking if the GP would ban all contract terms that aren't universally-reasonable. I don't think that's what they were saying, and it's not what I'm saying.

The purpose of unconscionability is clear, the question is what findings will trigger it? There is a spectrum of opinion on that. My position would be that, whenever it can be demonstrated by one court that a powerful entity did commit abuse via unconscionable contract terms, it should be noted by other courts and applied equally to other similar entities.

The US courts already do this, but the problem is they tend to take the narrowest possible application, and that's ultimately because they're deferential to the US Congress. They don't want to be making law, they only want to interpret the law they have. They want Congress to make law... but Congress doesn't seem very good at that. Most other country's systems are Roman law systems rather than Common law, which in practise means they tend to update laws and regulations more often, and the courts get their clarifications via updated laws rather than build up centuries of precendent.