Perhaps your CMS serves multiple front ends: a website, or a mobile app.

> Why would I want a CMS based on GraphQL?

The way I see it, the CMS is not based on GraphQL, it's just a CMS that you can query with GraphQL. I haven't used GraphQL at all, but it seems like it could be useful for working within a system where you need to bring data from many different REST endpoints together. Usually I would have to hand code something like this myself on the backend, but with GraphQL it seems like once you have it all set up, you can get data from multiple APIs, while specifying the schema of your response on the client instead of on the backend.

> What is wrong, with plain old HTML?

Nothing, if you can build what you want to build with "plain HTML" then do it.

Why?

Because they can pick the frontend stack they like! React, react-static, Gatsby, vue, nextJS etc.

You can pick the stack you like most. It is much easier to find a react developer than someone who knows how to write good drupal templates.

Why GraphQL? Because it's awesome! I can highly encourage you to just try out a GraphQL API and see yourself. It is designed for fetching related data efficiently and it will give you a huge boost in development productivity, which means lower development costs and faster time to market.

If you have lots of queries happening behind the scenes whenever someone makes a request that seems basic- like how Facebook gets a list of comments on a post, plus the friends who made them, and a list of different reactions to each comment, and other stuff that rapidly creates a complex graph- then GraphQL simplifies. The REST way involves all of those extra calls, GraphQL gets everything in one request.

Not specific to GraphQL, but plain old HTML doesn't work when other non-technical people are managing the content of the site. They need a GUI, and hence the need for CMS's in general.

What do you mean by this?