What made TikTok (and reels) effective was that it also added personalized discovery.
Most other social media services focused on showing stuff you that were either already subscribed to or were very similar to it. At some point, you would exhaust your feed. You more or less saw everything.
Of course, short videos are easier to scroll through than long YouTube videos but even to this day, the content of my YouTube feed has basically not changed in years.
I agree, Youtube still feels like "this thing held your attention once so that's what you get eternally". The "refresh your feed" option appears occasionally but it only makes things worse and shows you the raw fire-hose of humanity.
Most other social media services focused on showing stuff you that were either already subscribed to or were very similar to it. At some point, you would exhaust your feed. You more or less saw everything.
Of course, short videos are easier to scroll through than long YouTube videos but even to this day, the content of my YouTube feed has basically not changed in years.