“There must be a plugin for that” is often true. It does not always mean the plugin is right for your site. The decision should consider fit, maintenance, data ownership, performance, security, and what happens when the plugin changes.
Questions worth asking
Is the plugin actively maintained? Does it support the current WordPress and PHP versions? Does it add a large system for one small need? Can you export your data? Are the settings understandable to the person who will manage the site?
When custom is reasonable
A focused custom feature can be simpler when the workflow is specific, the available plugins are bloated, or the business needs a controlled integration. Custom does not mean building everything from scratch; it means owning the part that is genuinely unique.
Custom WordPress plugin development is a fit when the feature deserves a small, documented home in your site.