Oh, you mean setting up a state of the art web application? Years ago we had to roll our own pipeline, often building our own bundler and you had to use a ton of separate tools not meant to work together. There was no package manager so we had to download all of the stricts from random websites and hope for the best sticking them in a /vendor folder.
Nowaway you use the CLI of your favorite framework, type 1 command and you have an app all configured for a real world production environment. It's never been easier (and is easier than pretty much any other type of software development).
The only thing that changed is that since its so easy, you are expected to produce a high quality app if you want to be taken seriously. That part is hard.
Now you have a react app with a development up and running. To create a production build write "npm run build". To add a package write "npm install the-package".