While I generally agree that it's good to understand how tools work, I do wonder how far you think it is worth going. For example, Webpack uses a JavaScript parser called Acorn. Does one need to understand Acorn (and how parsers work in general) to build a React app? I would say no, although it is useful to some degree.
Acorn is on a lower level of abstraction than Webpack. Similarly, Webpack is on a lower level of abstraction than Create React App.
The way I see it, you can start from any level of abstraction that helps you be productive. Then you can start peeling back layers, and decide if understanding those is valuable to you or not. For example, understanding Webpack will help you create much more customized setups. But you can go deeper, and understand Acorn to work on support for new syntax proposals in Webpack itself. And so on.
I think it's important we don't insist some tools are "real" and some aren't. These are all different levels of abstraction, and as long as they help you solve the problem, they're all good. But I agree there is value in looking at what's beneath them when you have the time and need for that.