Most SaaS products have Vercel as partner, with Next.js and React as the tier 1 SDK on their tooling.
Not works in some of the cases and you have to implement fetch calls yourself, or some iframe boilerplate and JS glue, everything they expose in React is fully available in Angular, including field extensions, inline previews, sidebar extensions, the whole lot.
Invalidating the remark "I can't think of any serious company or project that would use this thing."
Where's the example?
React is designed with Next.js needs in mind nowadays.