Their algorithm dispenses a personalized feed that uses soooo much data from your watch preferences alone, regardless of it's permissions. This is so far ahead of user suggestion systems on other platforms, which are generally driven by collaborative filtering. Which inadvertantly is a stopgap for psychological exploitation of users. Other platforms plateau on their information gathering of profile due to the implicit conformity of the exchanges on social media. Not TikTok though.
I want to start by saying this isn't your Cold War sheen propaganda. This is Harmonious Society, "river crab" propaganda. This method can belie and camouflage the salient points of persuasion, sure. But it's not only intended to stream a deluge of coercive media. The purpose is to dominate the aesthetic discourse around topics, learning as much about you as they can, while ingratiating their clusters of community norms at the same time. There isn't a monolithic identity either. It's about picking the winners of our long form cultural evolution. Country to country data definitely shows varying preferences, but aside from the initial exposure to determine what clusters you associate with, these feeds are tailored heavily by user interaction.
The public description of their process divulges the use of object and character recognition, along with audio/tag keywords, to all items in a video. So even on a virtual machine with no app permissions, this site is making an incredibly detailed profile of your media consumption habits. For example, when you stop watching a video at a certain point, TikTok records what items were in it up to that point making you stay, and what audio/objects occurred at the point of losing interest. This catalog culminates as a set of meticulous preferences that end up correlating to all sorts of useful suggestion information; preferences for video formats(do you like dance videos, rants, or documentary content?), types of speech(language and culture obviously, but also intonation, volume, frequency of use, monologue vs dialogue), length and pacing, even framing of the camera, its all logged and associated with your device and you. Along with this, topics and community clusters are accrued.
This goes way beyond blanket brainwashing or disinformation propaganda in it's effectiveness. It's like if a personal interrogator was assigned to billions of people to know every minute detail of their personal media narratives. And at the same time, became a congenial friend who is coaxing all of them to subtlety shift their identities and preferences. Mass media always takes this trend to some degree, but TikTok isolates the individual's identity. (I didn’t write this lol)