There isn't a react engine because we don't see it as a good idea. The explanation is here.
We love reactjs. In fact we use it for all our UI. However there is no "reactness" useful when rendering static pdf or xlsx. That is why we stick with better DX provided by engines like handlebars. If we ever find or get recommend a good fit for react, we will happily use it.
However, if you have already a page with react reports, you can run it through the jsreport as well. The chrome-pdf recipe should process every html/js you send.