Plus, you can generally take the the dynamic generators and dial them down to a purely static build for sites that genuinely aren't using client-side features, but you can't go in the opposite direction.
I think for a startup with the liberty to choose a new tech stack, Nuxt.js is a great choice. It allows you to start with simple S3 bucket hosting, and move up to Vercel/Docker on ECS/etc. as you grow.
Hugo is a fantastic choice for blogs, but not for much else.