I’d love to live in a world where non-delegation was such a robust doctrine. But “you can set tariffs if you find that other countries are being unfair” (paraphrasing) is a more than intelligible principle supporting Congress’s delegation.
The case before the Court of International Trade failed on non-delegation and major questions grounds. But my point isn't that SCOTUS will affirm the lower court here (though: they will), but rather that your logic upthread doesn't hold. You said "the President makes foreign policy, not the courts". Plain category error.
Trump is knee-deep in negotiating with foreign countries on trade deals using the tariffs as leverage. And the court must purported to kneecap him. Of course it’s an exercise of the President’s foreign policy powers, and that’s why Congress gave the President this authority over tariffs in the 1930 act.
The major questions issue shows how out on a limb this court is. There’s currently a circuit split on whether MQD even applies to the president.