My nephew is totally addicted. He's 15 and recently visited me. He was on TikTok 24/7. I tried to watch a movie with him and throughout the movie he was still watching TikTok with one earbud for TikTok and the other ear for the movie. I really couldn't believe it. He stayed with me for a week and the phone was in his hand the entire time. I was pretty horrified.
I don't think it takes a certain kind of brain to become addicted. My nephew showed me a few videos and personally I found them boring, but that's because I'm an adult and I grew up in a world of long form content, stories with a beginning, middle, and end. I grew up with entertainment that required the viewer/reader to invest time in a story, to let it develop, to let characters develop, etc.
TikTok is the opposite of that. Kids growing up on TikTok have no appreciation for story. They're bored by dialogue. I saw that with my nephew. When we were watching the movie, I'd look over and see him absorbed in some stupid TikTok video, missing an essential part of the film, and I'd tell him to pay attention and he'd say "it's boring". Their brains are being wired to only want the payoff, the excitement, action, etc. TikTok (and other social media) is basically wiring their brains to crave constant stimulation and excitement. It's no wonder the whole generation is such a mess, heavily medicated, diagnosed with all sorts of mental disorders, etc. Any parent who gives his or her kid a smartphone with no restrictions or oversight might as well give them a loaded gun.