I've worked at 20 people companies and 2000 people companies, and can never recommend building a CMS. There are so many out there, and the one you build will just have a different limitation to the one you buy.

I second that. Any CMS-like system that you attempt to build with some customization will fail to implement some core elements of a CMS that you can adopt - be it versioning, publishing, workflows, etc.

Yes. Buy a CMS, and then cache the ever-loving shit out of it so it’s flaky slowness can’t affect your production delivery