This assumes that companies such as TikTok control their timeline up to the individual post, perfectly analyzed in order to extract your unique traits, and they have specifics ads lined up for you. Where - in my view - their timeline is just a bunch of random submissions. TikTik is just trying to sell ads and will try anything to match your profile to one of their active ad compaigns so they can bill their client more.
I'm confused at what you're claiming here. Yes, the submissions are rather random, but TikTok definitely figures out what type of content you like and what advertisements are most effective.
Your feed is almost certainly personalized up to the individual post, but I think if we are making an analogy to human curation it's certainly not working the same way behind the scenes.