People don’t like it because:

1. It’s the new thing. If alcohol were introduced today it would be banned in every country on earth. People tolerate Facebook, Twitter, Insta because that’s what’s been around. They all do the same thing, but TikTok is new and scary.
2. Short form video is scary! It’s a new form of entertainment, and old people don’t like new forms of entertainment. See: every newly introduced form of entertainment in history, books included.
3. They are misinformed about what data a mobile application can and cannot do, and the level of security built into both iOS and Android. Rest “assured”, they are collecting as much data as they can – just like every app creator on the planet. What they aren’t doing is capturing mic data while you’re sleeping (that’s not how microphones in phones work), stealing your passwords from your clipboard (OS’s notify users about clipboard paste)
4. China bad. This primes people to consider negative press about it with a less skeptical eye, feeding the above points. (Don’t misconstrue me as being pro-China, I’m not, and that’s not what this post is about.)