The problem is that for many, react does not do that – because you need npm, webpack, babel, systemjs, and so on and so on.
We come from a world where you have a simple .gradle config file, and you press one command, and it installs and everything just works.
No need to configure thousands of transpilers, no need to handle constantly breaking dependencies, because people keep their API stable for years, some even decades (see Bouncycastle, e.g.), etc.
Coming from this style of development where tech actually works well, and is stable, to the JS world of React where everything constantly breaks, is very complicated and over enterprise-ified, etc is quite annoying.
Obviously, on the other hand, the React world provides other massive advantages, such as quick iteration, innovation, etc – but the work to get something working with constant quality for years is entirely different. Because you’ll have to fork all your dependencies, because those won’t be stable.
So if you want your product to be included in Debian Stable, you don’t want to use React. Because you’ll end up forking and maintaining every single of your dependencies-.