Glad you asked Jose! Luckily, the create-react-app includes some npm packages that will help you with a few of your concerns. If you run the `npm run eject` command after creating a new test project, you can see which packages are included. For fetching data, I prefer to not use JQuery, I use the Fetch API and use a polyfill. The create-react-app tool includes this polyfill, so you can use the fetch API without having to worry about installing another package.
For promises the tool also includes this polyfill: https://github.com/then/promise.
I think the creators didn’t want to make too many assumptions about what tools React developers so they didn’t include every possible npm package you might need, just enough to get a basic application running. Hope that helps!