Medium is shockingly bad. I see absolutely no value in this service any more.
Simple example: with webpack it's trivial to configure it to load env-specific extensions. You can have foo.js, foo.dev.js, and foo.mock.js and it will import the correct one automatically based on an env variable. It's three lines of code that I use in all my React projects and it's honestly enough to keep me away from CRA.
[1] https://github.com/timarney/react-app-rewired/
[2] https://github.com/arackaf/customize-cra
[3] https://babeljs.io/blog/2017/09/11/zero-config-with-babel-ma...
FWIW Angular does the same thing with Angular-CLI. The "problem" is the web dev ecosystem, not React itself.