And what I'm saying is that Next.js does add the same complexity that you would add yourself but with great documentation. Also I have to say that's a very generic argument for any library.
Then why don't you just use the automatic code splitting of CRA?? And it's not generic, if you ever worked on a years old code base you are happy if complexity is low. Do you know if all the page transition libs will play well with Next? They do not play well even with react-router, the standard React routing lib. Code can be more complex than you might think.
SSR. CRA and Next.js are "templates" more than libraries with different aims. If you have specific arguments against SSR, just tell them because otherwise the discussion doesn't make sense.