Ask HN: How do people make proper sites with react?

It's been, 3 months since I started learning react. I can make SPA's do server side rendering with redux (i used express) but how do people actually use it for making proper sites, like pintrest uses react. For example, If I had to make KhanAcademy what would I do, react routing, basic auth etc are not going to work, how do people make actual working sites with these frameworks?