It's interesting that TikTok is a formidable competitor that focused on a different experience and a slightly different format (short form). Tiktok seems to work by choosing for you and only showing a single video at a time (esp on mobile, which is where it's really most at home), but allowing you to quickly reject that choice and learning from your rejections. Is it possible to beat YouTube itself with a different e…
So it's not the auto-play that's crucial, it's realizing that the user is giving you a signal. YouTube has been ignoring that signal. Perhaps it's a performance issue that makes them unable to?