You often hear engineers comparing Web Components with React. Here's my take on it.
Learning the HTML spec can be easy, even for beginners. Getting every browser and library to agree and support spec is hard. HTML is a living document and is constantly changing over time. Apple has refused to implement the customized built-in elements spec in Safari. All browsers have implemented custom elements v1 with the exception of Microsoft Edge where it is currently in development. We all just need to work together a little better and Web Components can provide a sustainable paradigm for implementing UI components heading into the 2020s.
This doesn't mean you can't start using Web Components today. Polyfills exist for browsers that don't support the spec.