Oh wow I just realized what the issue was: the file needs to be in the JS folder. I was placing it in JSX so that's why it wasn't finding it.

import MyData from "./data.json" works!

Thank you again for the help

I recommend to add a entry in the resolve section of the webpack config pointing to the root folder like this, so you can avoid relative paths

...
resolve: {
    modules: [SRC_DIR, 'node_modules'],
    extensions: ['.js', '.jsx', '.css', '.html', '.scss', '.less', '.json'],
    alias: {
        '@': path.resolve(SRC_DIR, 'js'),
        '#': SRC_DIR,
        config: path.resolve(SRC_DIR, 'config.js'),
        root: path.resolve(__dirname)
    }
},
...