This reductionism to "exposure to ideas" is absolutely absurd. TikTok and any other algorithmic feed isn't problematic because it exposes anyone to anything. They're problematic because those feeds can be used to actively shape behavior.
Shaping behavior is not very difficult if you have a lot of information about someone and control of what they see for hours a day. If shaping behavior didn't work no social media company would make the billions of dollars that they do. TikTok fads wouldn't exist if it was just a simple exposure to ideas.
TikTok in particular is worth targeting because of the way state security laws work in China. There's no legal issues with the state apparatus accessing company data. There's no judicial review. The state just has access to companies' back ends.
Since we know social media feeds can shape personal behavior and China can exert any control they want over Chinese companies, it's not a logical leap to realize a state hostile to interests of the North America and Europe having control over something people use for hours a day is a bad thing.
There's a whole cohort of the population for who TikTok is their primary source of "news". Their world view is shaped by what's presented to them. They're not "exposed to ideas" but targeted with specific narratives. Because all users have different targeting you may never see the same sort of feed as the person sitting next to you.