I like the ide of using wordpress as a backend service and then use a static file genertor to fetch the data from wordpress and then generate static files. Its how this blog is now woring with firebase and google cloud.
But before i started using firebase a build a small demo project to use gatsby to extract data from wordpress. I use i gatsby to connect to a wordpress and then generate html from it.
This demo is only a WIP so dont expect to mucth but its a nice tools to start woring integrating wordpress with gatsbyjs.