Gatsby is ridiculously fast (React based) and its plugin universe is full of all the common features you could ever need. It has built in 1-click service workers plugin for offline access, 1-click plugins for prefetching links you put on your page, auto-inlined-css (in v2), all kinds of markdown + fringe requirements like LaTex, video embedding, things like Call to Action plugins, MailChimp sign-up-here plugins etc. To get a feeling of the snappiness, check out their landing at https://www.gatsbyjs.org/ and their plugins here: https://www.gatsbyjs.org/plugins/ .
The community pushes and PRs at break neck speed every day and is super friendly - can definitely get the support you need. Lastly, it is a great way to "inverse learn React" if the objection is "Wow, I don't know enough React". React by itself is not that opinionated and Gatsby has enough good practices of putting together a React framework for you to use productively.
ps: the other frontend alternative would be vuepress, it should feel blazing fast too. Here's another article on why speed is so important: https://www.gatsbyjs.org/blog/2017-09-13-why-is-gatsby-so-fa...
Just wanted to point out that there are at least two kinds of fast: fast to build and fast to load. And while Gatsby-based sites are indeed very fast to load (although I haven't compared a Gatsby site with an optimized Hugo site), they are painfully slow to build.
But it is truly a pleasure to work with; that's for sure!