Sure. The implementation of React is orders of magnitude more complex than simply making a couple of HTML templates and sprinkling in vanilla js inside script tags, the implementation of sqlite is orders of magnitude more complex than simply de/serialising your data to a json file, and the implementation of nginx is vastly more complicated than simply exposing a web service directly to the internet.
Don't use tools unless you benefit from them. Some people benefit from being able to define JSON responses in a graph query language.
Maybe but the implementation is orders of magnitude more complex compared to simply making a couple of DB queries and then sending a JSON.