Custom development is useful, but writing custom code for a solved problem can be a waste of time and budget. WordPress has a mature plugin ecosystem, and a good existing plugin is often the right answer for common website functions.
Use established tools for established problems
Contact forms, SEO metadata, basic redirects, standard e-commerce, caching and many other common requirements already have mature solutions. A reputable plugin can provide years of testing, documentation and compatibility work that would be expensive to reproduce independently.
Evaluate the plugin, not just its feature list
Look at update history, support, compatibility, security record and whether the plugin is actively maintained. A plugin with hundreds of features is not automatically better. If the website uses only a small part of it, those extra features can increase complexity for both users and developers.
Avoid building a stack of workarounds
An off-the-shelf plugin stops being the easy option when it needs several add-ons, custom CSS, code snippets and awkward processes just to approximate the requirement. At that point, compare the total complexity with a smaller custom solution designed for the actual workflow.
Keep ownership and portability in mind
Where practical, choose tools that store content in standard WordPress structures and allow data export. Avoid making core business information dependent on a proprietary service unless the benefits clearly justify that dependency.
The practical answer
For common functions, use a proven plugin and keep the site simple. Move to custom development when the requirement is genuinely specific or when the “easy” plugin solution has become a complicated collection of compromises.