More data beats better algorithms. TikTok has vastly more interaction data by nature of its design. IG and YouTube shorts don't have nearly the volume of engaged users and are reluctant to disrupt the cash cow of their traditional interfaces.
I haven't worked on sites as big as YouTube but on sites with 100,000 members who are very much engaged with one "game" you usually find they are mainly indifferent when you offer them another "game" to play.
I like YouTube for what it is. I have interacted very little with shorts but Google has scarily seen into my imagination. I don't want to go into that rabbit hole.
Two populations can be similar in terms of conventional demographics such as age, gender, race, what kind of clothes they wear, etc. but be different in their behavior. IG users are "players of the Instagram game" and TikTok are "players of the TikTok game" and a whole system of values and behaviors are involved.
To take an example playing the "engagement farming" game on Bluesky I can follow people and know some fraction of people will follow me back, but who do I want to follow?
I postulated that the people I want are people who will repost my photos so I can try following people who repost photos but I find that reposters are not "followers" whereas I get a much better response rate if I follow people who follow another social media photographer since those people are "followers". People have an online behavior signature like that which for me matters more than the color of your skin.
It’s not just “did you click the like button”. It’s “did you swipe it away? How long did you watch until you swiped it away? Did you come back afterwards? Did you let it loop multiple times before moving on?”.
They’ll capture likes and dislikes you yourself probably didn’t even knew you had, just from tens and hundreds of these micro actions. And they’ll do it in the very first hour of you using the app, whereas YouTube won’t know too much about you even after months of you using it.