I am looking to develop a React JS web app, using react-boilerplate for development https://github.com/react-boilerplate/react-boilerplate
But the above boilerplate doesn't seem to be updated quite often, which boilerplate should be used for building simple web apps
There is not a simple good answer to this problem. Ideally, you should create your own boilerplate and maintain it over time, because only you will know what are your most common needs. There are no perfect boilerplates and almost every boilerplate is opinionated.
You might try to create a boilerplate for yourself from React CRA or other sources that might fit your needs in a great measure. It takes time in the beginning, but after a while you might update it every few months to make sure it is up to date and make it the starting point for all your new projects.
Sometimes a good point of inspiration would be the Yeoman Generators. Take a look here: Yeoman Generators