Web Components are great for doing multi-pass rendering with template placeholder substitution happening at multiple levels in the component hierarchy. The entire element HTML hierarchy can be declared in one place. It's extremely versatile. React cannot do this. It's difficult to explain without writing a whole essay but the benefits are very clear once you try this approach.
True, but at the same time if you're building an app the number of times when you think "I want to render this HTML without hooking it into the data store, other components on the page, data fetch layer, logging implementation, etc" is literally zero. React can't do the thing people building apps with React never do is not an argument against React. React is for building React apps, in case that wasn't obvious.
Multi-pass rendering with multi-pass template placeholder substitution is very useful because you can have an entire complex component hierarchy declared in one place, very succinctly, in one file... Different components in the hierarchy can render data at any depth below them in the hierarchy (any level of nesting) without child components having to know about it. The child components just take the partially pre-filled template as their input and fill in remaining placeholders. The logic/markup is much more succinct and the components are much more flexible and composable. It promotes better separation of concerns.