Good site architecture is quietly one of the highest-leverage SEO moves available. It helps search engines understand what your site is about, spreads authority to the pages that need it, and makes the site easier to use.
Keep it shallow and logical
Aim for important pages to be reachable within two or three clicks of the home page. Group content into clear topics, and let URLs reflect that structure rather than burying pages deep in the hierarchy.
Internal linking with intent
Link from supporting blog posts up to the service or pillar pages you want to rank, and from those hubs back down to the detail. Consistent, descriptive anchor text tells search engines what the target page is about.
Set it up cleanly in WordPress
Use categories deliberately, keep permalinks short and readable, and add breadcrumbs so both users and crawlers always know where they are. Done well, architecture keeps paying off long after the initial work.