This is usually argued as a matter of taste. It is actually a matter of who edits the site, how often, and what it has to integrate with.
What WordPress is genuinely good at
A large team publishing frequently, a content-heavy site, or a business that wants to hire an editor tomorrow from a very large pool of people who already know the interface. Those are real advantages and they are worth a lot.
It also has an ecosystem for almost everything, which shortens timelines when a requirement is common.
Where it costs you later
- Speed. A page builder plus a dozen plugins ships weight to every page. Achievable performance drops, and getting it back is a project of its own.
- Maintenance. Core and plugins update constantly. Skipping updates is a security problem; applying them without staging is an outage problem.
- Security. Popularity means it is the most probed platform on the internet. Manageable, but it is a standing cost.
- Drift. Five years of plugins accumulate into something nobody wants to touch.
When a custom build wins
When the site is mostly fixed and needs to be fast: a brochure site, a campaign site, a high-traffic landing environment. Hand-built pages load in a fraction of the time and there is nothing to update every Tuesday.
Also when the logic is unusual. Custom booking flows, calculators, unusual catalogue structures or a deep CRM integration are often cheaper built directly than bent into a plugin that nearly does it.
How to decide in one question
Who will edit this site, and how often? If the answer is "our marketing person, weekly", a CMS earns its overhead. If it is "almost never, and we will call you", a custom build is faster, safer and cheaper to own.
That is the conversation we have at scoping, and the answer changes what we quote. What does not change is the build spec: the load time and accessibility targets apply either way.