A few months ago we decided to move our whole static website (www.algolia.com) to a new stack. At the time we were using a website generator called Middleman, written in Ruby. As a team of only front-end developers we didn't feel very comfortable with the language itself, and the time it took to build was not satisfying. We decided to move to Gatsby to take advantage of its use of React , as well as its incredibly high performances in terms of build and page rendering.
Did Gatsby affect your SEO in any way? We're in the process of redesigning our website and the choice was between Gatsby and NextJS. The team was worried that using Gatsby would affect our rankings as there's no SSR so we ultimately decided on NextJS
I'd recommend looking at netlify cms too! It's a cms which writes to your SCM to update the codebase for non developers :)