You and I, we're nobodies with no power. We share a country with people who do have power. The power they exercise impacts our lives. Those people have weaknesses. Those weaknesses can be exploited.
If you ran an intelligence service, you might want to identify targets, prioritize targets, and potentially create a graph of social connections.
Tiktok provides picture data (geolocation, timestamps, hashes, potentially facial recognition and OCR), location data, time data (hours app is opened), private message data, and data on hobbies/interests, I assume there is profile and private message data as well.
That's all without bringing up the glaring problem which is damaging institutional trust. Promoting anti-science videos or showing one group very pro videos and another group very against videos is damaging to our very social fabric. Amplifying things that feel intuitive but aren't correct is dangerous.
The threat model you perceive is that our authoritarian government would oppress us. The threat model that is happening is that external governments are causing chaos within our borders, amplifying division, and sewing distrust.
You perceive the government to be a bigger threat because of how you imagine you might exercise power, maybe you want to unionize, maybe you worry about police abuse, maybe you worry someone might take your guns, maybe you hate taxes. That misses the bigger picture... out of the following people, would you prefer them to be "compromised" by the CIA or by China? Soldier, Politician, Judge, CEO, Engineer, nuclear scientist, EPA regulator, Chief logistics officers, FCC employees, Bankers, etc.
I think the answer is pretty obvious, but I'm open to an explanation of why it is not.