WordPress is the right default for the large majority of content-driven sites — but “large majority” isn’t “all,” and knowing the exceptions matters before committing either way.
Why WordPress wins by default
A mature plugin ecosystem, a huge pool of people who can maintain it, and content modeling flexible enough for most business needs out of the box. For most marketing sites, blogs, and even many e-commerce stores, there’s no good reason to build a CMS from scratch when WordPress already solves the problem well.
Where a custom CMS earns its cost
Highly specific content models that don’t map cleanly onto posts and pages — a real estate listings platform, a course catalog with complex relationships between content types — can end up fighting WordPress’s data model more than benefiting from it. Extreme performance or security requirements, where the surface area of a general-purpose CMS and its plugin ecosystem is itself a liability, are another legitimate case.
What you give up by going custom
The plugin ecosystem, the familiar admin interface your team may already know, and the large pool of people who can maintain a WordPress site versus a bespoke one. A custom CMS means every piece of functionality WordPress gives you for free now has to be built and maintained by you.
The actual decision
If your content model fits reasonably well into what WordPress (or another mature CMS) already offers, use it — the time saved is substantial. Build custom only when there’s a specific, well-articulated reason the existing options don’t fit, not as a default preference for “something built just for us.”