Can I use web components in react application?

Yes, you can use web components in a react application. Even though many developers won't use this combination, it may require especially if you are using third-party UI components that are written using Web Components.

For example, let us use Vaadin date picker web component as below,

import "./App.css";
import "@vaadin/vaadin-date-picker";
export default function App() {
return (
  <div className="App">
    <vaadin-date-picker label="When were you born?"></vaadin-date-picker>
  </div>
);
}