It is more a bad large-scale societal outcome that many are worried about. It is a massive CCP-linked propaganda organ; even if content is generated by users, the way in which it is surfaced and promoted is entirely controlled by ByteDance (-> CCP). Furthermore, all sorts of social engineering, spear phishing, and blackmail by a potentially-hostile foreign government are made possible.

But if you want something to worry about as an individual, consider China's increasing global reach and whether the CCP could at any point use their massive reach to systematically make life less pleasant for you if you express views contrary to the party's.