Also, an option to do full-screen would greatly enhance the experience.
I think the biggest issue that exists with current YouTube is that so much is crammed into the UI and viewing experience (Ads, the videos on the sidebar, clunky controls to skip videos, etc...) that ruins the continuity of video content, especially when mixed with so many videos in different formats... It's also the same problem that TikTok is fighting with, it makes for a pretty disruptive viewing experience in comparison to cable TV or just choosing to watch TV shows or movies instead.