Do you have anything specific in mind?
Any kind of downleveling, though that's less important these days most users only need polyfills, new syntax features like `using` are not widely used.
Minification, and bundling for web is still somewhat necessary. ESM is still tricky to use without assistance.
None of these are necessary. But if you use any of them you've already committed to having a build step, so adding in a typescript-erasure step isn't much extra work.
No Lit Element or Lit or whatever it's branded now, no framework just vanilla web components, lit-html in a render() method, class properties for reactivity, JSDoc for opt-in typing, using it where it makes sense but not junking up the code base where it's not needed...
No build step, no bundles, most things stay in light dom, so just normal CSS, no source maps, transpiling or wasted hours with framework version churn...
Such a wonderful and relaxing way to do modern web development.