What's more, if you want it to only do this when passed new props and not at other times, you have to use things like React.memo:

"If your component renders the same result given the same props, you can wrap it in a call to React.memo for a performance boost in some cases by memoizing the result. This means that React will skip rendering the component, and reuse the last rendered result."

https://reactjs.org/docs/react-api.html#reactmemo

But it doesn't do this is my whole point. React will not blow away the entire DOM in the document even if props change.

It will correctly keep your scroll position, caret position, etc. if you use React the way it's intended to be used, which is very easy to do and learn. Of course if you use the `key` prop to blow away the entire DOM with every change all these benefits are lost, but thats not react's fault, its your own.