The thing that I don't like about web components is that it's a browser specific technology. With React, I can render the first page on the server, so the user doesn't have to wait 3 seconds for the initial page load. So I'm not a huge fan of anything that's browser specific and can't be rendered on the server. I see why Google is pushing for it - web components would mean crawlers not having to execute Javascript, which translates to significant savings on crawling infrastructure. But it'd make for a shitty user experience.