A WordPress theme controls far more than colours and fonts. It affects layout, performance, accessibility, editing experience and how difficult the site will be to maintain several years from now. The right choice depends on the website, not on whether one approach is fashionable.
Commercial themes are useful when the requirement is conventional
A reputable commercial theme can be a sensible choice for a straightforward site with a modest budget and common layout requirements. It can reduce initial development time and provide pre-built components that would otherwise need to be created from scratch.
The trade-off is that general-purpose themes are built to satisfy many different users. That can mean extra CSS, JavaScript, options, templates and third-party dependencies that your website never uses.
A custom theme gives more control
A custom theme can be built around the exact content and components the site needs. That usually makes it easier to keep the front end lean, make the editing experience match the client’s content, and avoid layers of configuration designed for unrelated types of websites.
Custom does not mean every element needs to be invented. WordPress itself provides mature block-editor tools and APIs. The goal is to use the platform well and add only the project-specific pieces that are needed.
Avoid theme lock-in
Whichever approach is used, important content should not disappear if the visual theme changes. Content types, business logic and critical data should be kept separate from presentation where practical. This is one reason custom functionality often belongs in a plugin rather than being buried in a theme.
Think beyond launch day
The cheapest or fastest way to assemble a site is not always the cheapest way to run it. Consider how often the theme is updated, whether its dependencies are well supported, how easy it is to edit content, and whether the site can be modified without fighting a complex framework.
The practical answer
For a simple site, a good commercial theme may be entirely appropriate. For a long-lived business, municipal or organization website with specific design and content requirements, a focused custom theme often gives better control and a cleaner maintenance path.