To be fair, v5.9.0.13 lacks many current staples:
In the fast-paced world of technology, software updates are relentless. Each week, developers push new code to squash bugs, introduce features, or—most often—redesign the user interface. For YouTube, this evolution has been dramatic: from a simple 480p video player to a behemoth of Shorts, podcasts, livestreams, and shopping integration. youtube version 5.9.0.13
Users could continue watching a video in a small window at the bottom right while browsing the rest of the app, a revolutionary feature at the time. User Experience Review Pros: To be fair, v5