It's super popular. My son started using it and it roped in me and my wife. Of my son's peer group, everyone uses it. Like virtually every kid. I completely believe those numbers.
I know a lot of TikTok users that are my age (~36). It isn't my peers that work as software engineers at tech companies; it's more "normal" people that I have met through Discord communities.
(I don't mean it's abnormal to be a software engineer or anything, just that we're overrepresented on HN. This is our social media. I don't use or enjoy TikTok.)
The closest thing to IRC/chatrooms of Web 1.0 by how it feels.
Yes, beats even Discord.
Like, remember the days where you could just go online and bump into random people, and it would be interesting? And you could just throw an ugly homepage with your dog and "under construction" gifs without thinking twice, just because it's fun?
Happy to run into people who recognize how delightful it is. I've seen so much variety if the videos on my fyp page (how to start a locomotive, how to move between high voltage transmission lines, woodworking tips, etc.. It's a amazing. I thoroughly enjoy Tiktok and don't feel like I've wasted time even after scrolling through it for an hour.