Page speed is key. You can see in search console how changes to page speed effects how often a page is re-indexed and how many pages are indexed. For some sites that does matter. It basically comes down to how much money Google will spend on your domain.
If you need your site to be indexed by Google it should be very close to plain HTML and CSS with pretty much no JS that changes the DOM at all. The Venn diagram of 'pages that need fast DOM updates' and 'pages that need to be indexed by Google' should really be two separate circles... That's why I suggested SSR or SSG.
There are very few React+backend websites that need the content to be indexed by Google. That part is important. The overwhelming majority of React code is sat behind a login page that Google can't get past.
Anywhere an app is serving public content using React it should be using some sort of server side generation with hydration and progressive enhancement, which entirely negates the need for a fast VDOM for SEO reasons.
