The optimizations Gatsby does by default are great, especially if you're a web performance noob. But, I feel like Gatsby and static website generators in general are the product of front-end developers learning to code Javascript with no knowledge of HTML or the underlying technologies.
Nothing wrong with having a chance to make a website with your favorite front-end framework, but when you've been doing web apps with Javascript and websites with only a CSS framework if any, these generators just feel like a bit too much. Not everything needs to be an "app", if you catch my drift.
If you want to make a website that's blazing fast and you happen to know React well, Gatsby really is your best bet.
Nothing wrong with having a chance to make a website with your favorite front-end framework, but when you've been doing web apps with Javascript and websites with only a CSS framework if any, these generators just feel like a bit too much. Not everything needs to be an "app", if you catch my drift.
If you want to make a website that's blazing fast and you happen to know React well, Gatsby really is your best bet.