We need it all including overall UX, UI design, dev, tech writing, graphics, SEO and ops. Therefore tempted to consider an agency (our team is focused on developing our product and supporting our customers - we can't be distracted by the website).
On the other hand, communicating our product requires skilled technical writers, and likely domain expertise in open source, secure networking, DevSecOps and XaaS. The types of folks we may be better off adding to our team directly.
All that said, we don't have much experience with this. Thoughts from those who are more expert? We could of course go with a hybrid model as well - hoping to learn from what you have learned, while recognizing there is a YMMV component to this.
My 2 cents, use wordpress, hire an agency and have them set it up so your team can add the technical articles, posts etc as needed but get the crux of it done using an outside resources that specialize in doing that kind of work.
Most good agencies also have copy writers and some even have tech writers as well. You can setup topics, give them specific goals for each article to write that then you just wordsmith, but the initial time consuming part is done for you. There are agencies that specialize in almost every industry, just look for one. And if not this is where your team can step in to help craft the articles/content themselves but not have to worry about the design & dev of the site.