In this post Helen Hou-Sandi suggests working on starter content to the new Twenty Seventeen theme. UX should be a major concern in all themes:

“While theme review guidelines need to be finalized and documented, it is anticipated that themes being submitted to WordPress.org will be expected to select from core-provided content to promote consistency and to help keep the theme review process from becoming lengthier, with exceptions being made on a case by case basis. Themes being distributed outside of WordPress.org are not subject to the same review process; however, it is recommended that consistent user experiences be the primary consideration in how starter content is chosen and implemented.” (HHS op.cit.)