I do think TikTok is a site that people find themselves clicking and sitting on, but I don't think the right words is "addictive". Let me explain.
University of Brown did a study on the addictive parts of TikTok
https://sites.brown.edu/publichealthjournal/2021/12/13/tiktok/. Within their explanation, they explain how "once immersed in the flow-like state, users may experience a distorted sense of time in which they do not realize how much time has passed." I would not use that piece of evidence to prove addiction, rather to prove that people get very caught up when they are on their phones.
There is a joy that is found in a lack of responsibility. When people are scrolling, they have no responsibilities and are simply scrolling endlessly and laughing. Personally, I scroll for hours. Each video is usually no more than a minute long, so it feels like I am wasting no time. It seems harmless in the moment, and then 45 videos later I realize I have been scrolling for way too long. The thing with addiction, though, is that it is something you crave. I would say I have a pretty addictive personality, and I can say I don't crave TikTok. When I am bored or doing nothing I open it up and scroll, but when I have something to do or am occupied, I am not sitting there craving TikTok.
I discussed this with my peers. They all had similar mentalities to me as TikTok not being addicting, but rather engaging and sucks you in. You can scroll and scroll and new content will continue to come up. I also think this can depend on the person, but I would not generalize TikTok as an addictive platform.