The one-page site still wins

The case for a multipage site is usually made by the person building it, not the person using it. Navigation adds complexity that only pays off when the content genuinely requires separation.

A single page forces editorial discipline. You can't bury the weak section behind a nav item — everything is visible, and the hierarchy has to actually work. Hierarchy is a content decision, not a layout decision. Mobile-first just makes you confront it early.