Using React is really bad for your SEO. If you want to use React, use something like Nextjs or Gatsby to compile it into a static HTML website.
Gatsby doesn't compile to a static HTML website. It compiles to a static site. There's a subtle difference. The pages are rendered on the server and served as static assets, but the entire React routing and content loading is still there. When a visitor loads a page it renders and then gets turned from plain HTML back in to a React again. When you navigate from one page to the next all the content for further pages is preloaded. You are not loading a full HTML page for each link you click on (which is exactly what makes it feel so lovely and fast - everything is being preloaded behind the scenes).
And Google has started to index SPAs[2] as well even though it's not instant like others have mentioned.
[1] https://reactjs.org/docs/react-dom-server.html#rendertostati...
Google bot runs JavaScript these days. I'm sure proper SEO is possible in the worlds most popular UI framework.
If SEO is a critical requirement, I'd recommend either server-side rendering (SSR) through a framework like Next.js or completely static sites through whatever framework you prefer (Next.js, Gatsby, 11ty, Hugo, Jekyll, etc, etc).