> If I can't just include a file things are going to get more complex.
But the tooling and npm packages are all optional. You can import React from a CDN and use stuff like htm [1] or domz [2] instead of a JSX compilation step.
Or you can use Vue instead of React (their tutorial starts by using Vue via CDN).
If you're able to only support 95% of the browsers, you can use most modern ES6 features, including ES Modules and async/await.
If you still need the tooling, there are options like Parcel [3] or Poi.js [4] that require zero configuration. You don't really need the complexity of Webpack.
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[1] https://www.npmjs.com/package/htm
[2] https://www.npmjs.com/package/domz