It's not React only. It has pure/regular HTML, React, and Vue. I have mainly only used the pure HTML personally as I use Phoenix/LiveView for most of my stuff, and it works phenomenally well and is very copy/paste friendly. The UI/console they provide is also top notch. For others who do use React, the React stuff also worked well too for one project I did that was a SPA.
It's well worth the money IMHO.