The featured themes list was deliberately excluded (along with popular themes) from the theme browser in the customizer that shipped with WordPress 4.9 over two years ago. That interface defaults to latest themes and emphasizes filters and search. Only the legacy theme browser in wp-admin still has the featured themes list. It remains part of the wp-admin section that is functionally replaced by the customizer but still exists for political reasons.

The long-term goal was to improve the theme discovery experience through a refined approach to filtering, and by unifying theme browsing/switching with other site management and customization workflows. That work could pick back up with limited technical challenges if interested parties can agree on an approach.