To me this is the "emperor has no clothes" about the whole ecosystem. The actual users don't care if it's a static file, a database CMS, or a herd of cats running around frantically typing up HTTP responses. So it's odd to me that the big selling point is "we did something neat in how we made our product!". Right, but what does it do to make your users life better than using ghost or wordpress, or whatever?
I know that some devs see it as a rails like thing to combine with graphql, but if I was going that route I personally wouldn't start with something that's ostensibly a static site generator.
Basically, the hosting can be unbundled from generating the site. And this is the territory which big companies like Amazon, Google, and Microsoft are already good at.
of course, Gatsby cloud won't want that, and the only way to solve that problem is to create artificial lockins. And when they do so (because they need to justify their valuation), people will leave.
There's indeed little magic involved so Gatsby has to do a really good job to keep customers both integration and speed wise.