The UI of the default Open edX LMS front page of courses (generated by edx-platform) is limited. It was created back when we had four courses on edx.org, and it doesn’t work well for browsing a large catalog.
For various historical reasons, students who go to www.edx.org see a Drupal site that is proprietary to edX. Over time, we’ve been steadily pushing more of the course discovery logic into open source components, and the current course browsing experience uses the course-discovery service. The UI shell at https://www.edx.org/course?course=all is still being served in Drupal, but the browser is making API calls to course-discovery to get all the information.