Before: Chain together style-loader, css-loader, postcss-loader and the MiniCssExtractPlugin in some weird way. So complicated to understand which PostCSS plugins interacts with resolving imports. I often need to look into the webpack.config.js to understand how everything work. After: Use PostCSS and its tooling for CSS. Yes, there's now a separate process I also need to run in order to watch and build CSS. Yes, I can no longer `import "./style.css"` from the JavaScript files. But it's so much easier to reason about! The CSS tooling creates a CSS file; the JavaScript tooling creates a JavaScript file. Do I want to build SVG sprites? Well, that can very easily be a separate script which I can debug independently and _not_ couple into my builder's plugin system.
In addition, now my JavaScript files are actually just JavaScript and I can be pretty sure that it will work with any new tooling without any problems. Once the successor to ESBuild comes out I will most likely be able to point it at index.js and everything will work.
That's been my feeling for years, too: if your team is less than, say, several dozen people there's a significant amount of merit to having something which doesn't require continous care and feeding for anyone to work, especially when it's combining a number of complex libraries with independent development teams.
As yet another tiny UI framework creator (forgojs.org), the switch to esbuild-loader was our best developer experience decision. create-forgo-app (our CRA equivalent) takes 3-4 seconds, and running it is instantaneous. Faster builds actually change the way developers write code.
It’s smart though. Despite having built webpack plugins myself, my main gripe with it was how overloaded it became.