I used Gatsby about a year ago for a personal blog, but ended up abandoning it for the following reasons:
- Very slow build times. It took me over a minute to build a personal blog.
- Weird forced implementation of GraphQL. To display something as simple as an image I was forced to use GraphQL. Also your GraphQL can't be dynamically generated, meaning it's hard to make anything modular. And the GraphQL paths has a ton of extraneous nested fields (eg. `data.file.childImageSharp.fixed`)
- Version upgrades were a pain in the ass and would often break my site.
- My site actually seemed slow. For example, links don't work until the entire JS loads and executes, so if your internet isn't fast then your website basically isn't functional for the first 2-5 seconds despite the page being visible.
- Very few themes (maybe be better now, but at the time the selection was awful, especially compared to Jekyll). No real concept of themes in the first place, switching from one theme to another requires an entire code rewrite.
- Limited functionality built-in. For example, want tagging? You'll need to code that in.
Gatsby sits in an odd spot of not being simple enough to save you a lot of time or empower a non-technical person to manage (eg. like WordPress), but not flexible enough to do anything you want since it's an opinionated SSG framework. It's like you're getting all the complexity of a React/GraphQL application, without any of the flexibility of being able to pick your own stack.
Sure it has a nice plugin system, but beyond that since you need a developer to set up and maintain a Gatsby site anyways, I don't see any reason not to just use Next.js (which can export to static) since all Gatsby really does beyond that is converting markdown to HTML, which is just done through an npm library anyways. If writing a Next.js website is overkill, then why do you need to be devoting engineering resources to this in the first place? Why not just use some no-code solution like WordPress? Or if you really want a separate headless CMS, then Jekyll felt easier and faster to me with more theme options (though again it's been a year since I touched these, so I imagine things have improved).
Don't get me wrong I love SSGs as nothing beats the performance, ease of deployment, and low cost of static sites. But if I'm going to use a SSG framework, it better be dead simple and/or easy to customize, otherwise I might as well just use some off-the-shelf "no-code" solution (eg. WordPress, Wix, Squarespace), or use a framework like Next.js that let's me customize my stack instead of being locked into Gatsby's. Gatsby's $200m valuation makes absolutely no sense to me unless they're planning some drastic changes I'm not aware of.