Well, React in and of itself doesn't, sure, I agree. However, if you look at React code, from the Getting started to ANY example out there, they do all have a "structure" that easily identifies it as React code and each file has an inherent structure that I can easily split up in my brain to understand what's going on. So the use of React ... comes with ... some form of often-repeated structure/patterns.
It absolutely defines a standard for what a "UI Component" is and how its behavior should be orchestrated by the APIs React provides.
What it doesn't provide is a way to manage complex state that persists beyond the scope of one component (Context isn't good enough), and every single app has state that persists beyond the scope of one component