In order to get that freedom, you need to build the tooling in such a way that it aligns with the web standards, so that when the standards catch up you can drop what you don't actually need anymore. We all switched from coffescript to ES6 and Babel because ES6, being standards-based, will eventually be supported in browsers, right?
And yet, with JSX we have a gratuitously non-standard dialect of JavaScript that isn't on the standards track and will never be natively supported in browsers. So, even when browsers catch up and offer full support for modern ES6 syntax, we're still stuck with transpilers because Facebook thought it was a good idea to tightly couple their custom templating language to JavaScript itself instead of wrapping it in template literals, which is the standards-based approach that ES6 actually provides for embedded DSLs and templating.
Today, in Europe and North America, roughly ~85% of users run a browser version that has native ES6 support. IE marketshare fell off a cliff in 2016, and now IE11 is at less than five percent and still falling. I don't actually need to transpile during development today, and I won't need to do it in production either in a year or two, and yet everything written with JSX will need a transpiler forever.