I write a lot (in Japanese) on the web and have had some meaningful traffic. I think the most I got on a single day is like 150k visitors. And I've tried everything from raw HTML to SSG to Wordpress to a homegrown CMS.

The truth of the matter is, for most web writers, any CMS is plenty performant. You probably won't even need a cache, and if you end up needing one, it's usually pretty straightforward to add it. And it's pretty self-evident to me that updating one document and saving it is easier than re-generating the updated parts of your website with some script before git-this-git-that.

One good argument against CMS is security: many of them have a history of security woes. This is partly why I ended up writing my own very minimal CMS engine. All it does is read some markdown files and render them. For me, that achieves both security (or at least if not, it's easier for me to go through my 100 lines of Ruby code than the Wordpress codebase) and low friction.