Drupal is not just a way to easily manage large amounts of content, it actually helps you keep that content organized and structured as well. This is a terrific asset to your SEO campaign. Search engines want to know what your site is all about: primary topics, subtopics, related headings, and so on, all help. By using the built-in Drupal tools, your site can be in top shape for the search engines.
There's a reason you learned the outlining format in grade school. It's easier to organize related ideas when they're structured hierarchically. It turns out that it's easier for search engines to figure your site out when it's structured that way as well. So, send a long-overdue thank you note to your fifth grade language arts teacher and let's get organized.