This is a rather perplexing statement to make.
If anything, Redux only plays a role in adding syntactic sugar over React's support for reactive programming.
More importantly, the general guidelines are that you should only bother with Redux if your SPA is already considerably complex.
Redux doesn't have anything to do with any kind of syntactic-sugar for Reac.
> the general guidelines are that you should only bother with Redux if your SPA is already considerably complex
If one already has an (non-React) SPA which is not already built following Redux then you're stuck with what you've got; it isn't really possible to take an existing SPA of any complexity and deciding to "make it use Redux" because it completely up-ends practically every aspect of SPA application-design, at least as far as how "traditional" (non-React) SPAs do things.
If you'll permit me to oversimplify: I tell people that React is a basically an opinionated Redux kernel wrapped around a JSX-based DOM+component/widget system (, which then means you now need a JS build system too); or conversely: Redux is like React, except without JSX components.
...or am I misunderstanding you?
This is simply false and is outright wrong. This even goes against the most basic React+Redux guidelines. Dan Abramov, one of the creators of Redux, is quoted in Redux's FAQ:
> would like to amend this: don't use Redux until you have problems with vanilla React.
https://redux.js.org/faq/general
> it isn't really possible to take an existing SPA of any complexity and deciding to "make it use Redux"
Frankly, you sound as if you have absolutely zero experience with React. I know for a fact that a few flagship SPAs from a few companies, including some FANG webapps, do not use Redux.