There Isn't a Universally Right Answer
Agencies often have a strong preference here, and that preference frequently reflects what they're set up to build rather than what suits your project. Both approaches are legitimate; they suit genuinely different situations.
Here's how the tradeoffs actually break down.
Where WordPress Makes Sense
WordPress and similar platforms handle an enormous amount of common functionality out of the box — content management, user roles, basic SEO structure, plugin ecosystems for almost any standard feature. That means less gets built from scratch, which generally makes projects faster and less expensive.
It fits well when your site is primarily content-driven, when you need non-technical staff to update content regularly, and when your requirements map reasonably closely to what the platform and its ecosystem already do well.
Where Custom Development Makes Sense
Custom development means building more from the ground up. It typically costs more and takes longer, but it removes the constraints of working within a platform's assumptions.
It fits when you have genuinely unusual requirements — complex pricing logic, specific workflow automation, deep integration with existing business systems — or when performance and control matter enough to justify the additional investment. Forcing these into a platform through layers of plugins often creates more long-term fragility than building properly from the start.
The Maintenance Difference Nobody Mentions
WordPress sites need ongoing updates — core, theme, and plugins — and outdated plugins are one of the most common ways sites get compromised. That's manageable with a maintenance plan, but it's a real ongoing responsibility rather than an optional extra.
Custom sites have fewer third-party dependencies to update, but when something does need changing, you generally need a developer rather than being able to install a plugin. Neither is lower-maintenance in absolute terms — the work is just different in shape.