Executive agencies have to obey the Administrative Procedures Act which is not a high bar and yet the current administration doesn't always manage to clear it; it has had several policies turned back by SCOTUS for not being able to come up with a facially valid reason.

Sure, the executive has constitutional powers, but the powers used in this WeChat ban come from the National Emergency act and the International Economic Emergency Powers Act, not the constitution. So I think the misunderstanding comes from the fact that you’re talking about constitutional powers, which are not at issue here. Powers created by legislation are constrained by the statutes themselves and Administrative Procedure Act requirements.