Even if TikTok doesn't currently know too much about you[1], there is very little to stop the Western-facing version becoming as much a sucking database of incidental and incremental information gathering as Douyin appears to do (directly for the CCP) in mainland China.
Apparently, TikTok traffic has exceeded that of Google. Not sure if that's per-instance, or video bytecounts help, above most of the more trivial infofeeds/sinks of Google's widespread tentacles, but getting anywhere near Google's already non-trivial penetration of our lives needs a lot of consideration.
Really, the problem is primarily oversharing, not unique to Tiktok. And there's Facebook, TwiX and the rest (Microsoft's actually worse than it was, in the days it was largely unopposed in its sector of the market, and I normally have little experience of Apple but I cannot believe that they have not had a lot of the same stuff already in the bag). But I don't think ByteDance has even pretended to subscribe to the motto "Don't Be Evil".
Some of it may be (over)abundance of caution. But there's plenty of reason to suspect that it is not a stretch to imagine strategic surveillance filters its way towards a not-exactly-friendly regime.
From my own past experience in data-security, I'd go nowhere near it. It helps that I don't ever feel my need to shake my bare booty while lipsynching to K-Pop (and, thankfully for everyone else, certainly not to let other people see me do it). If I was (say) in the US government and had a need to "get out there and 'connect wid da kids' over my latest thoughts regarding 21 CFR Part 11" then I'd get myself a dedicated device (and separate accounts/backup contact details) rather than put it on my personal device or (especially) an official government device that's probably tied strongly into officially secure channels. I wouldn't take it with me everywhere, or even keep it switched on. I'd schedule specific times, places and contexts when I'd make use of it (copy across video, if necessary, making sure the meta-information that went with it was shorn of anything not necessary), and maintain a sanitary gap both for security and my own peace of mind. But I'm perhaps more properly-paranoid than others.
The biggest protection that any current social-media user has is (despite everything) "security through obscurity". With so much data flowing around, there are probably surprisingly few "must grab" profiles identified by the owners of the various servers. Where not only is every possible byte scraped, out of whatever collection system exists, but that it finds itself being rigorously scrutinised at the actual desk of who-knows-who on behalf of 'interested' parties.
[1] Often with voluntarily provided information, including making videos that locate you, identify your family/friends/vehicles, whether or not you make them globally visible. Not to mention revealing your rather specific minks, fetishes and 'weekend activities'; if not by recording you doing them, but by letting The Algorithm know that you're interested in others who do.