I don't think it's correct to claim CRA and its peers are against code splitting. Dynamic import is a well-documented way to achieve this:
https://facebook.github.io/create-react-app/docs/code-splitt...
https://facebook.github.io/create-react-app/docs/code-splitt...
You need to make a business case that your whole application is modularly composable.
Some application might fit under this umbrella, but there are other stuff that don't, like a pdf-render, or something like google slides, which as I just checked, the core editor js is bundled in a single js file and as large as 1.4MB.