I think it's just broken in some cases for whatever reason. Like 9 months ago I mentioned trying out Tik Tok for some weeks and despite lots of "not interested", likes etc, I got swamped by 99% garbage, including videos I specifically said I don't want to see.

TikTok has lots of content for nerds (though I think they prefer the term neurodivergent). But there is certainly a trend that TikTok content is comparatively shallow. For example Hank [1] and John Green [2] have quite nerdy content, but it's much shorter less developed thoughts than their youtube channel [3]. Or NileRed: his most recent TikTok[4] (eating capsaicin) is in no way comparable to his most recent YouTube[5] (synthesizing cotton candy from cotton balls). In terms of nerdy content it probably shines more with life advice than with science facts, simply because of the short video format.

Not sure about the age group, most of TikTok is probably targeted at ages 12-40.

1: https://www.tiktok.com/@hankgreen1?lang=en

2: https://www.tiktok.com/@literallyjohngreen?lang=en

3: https://www.youtube.com/c/vlogbrothers

4: https://www.tiktok.com/@nilered/video/7063145462794145030

5: https://www.youtube.com/watch?v=vHuFizITMdA

I found that my initial foryou feed was pretty terrible and I ended up in political content pretty quickly. Once I nudged the algorithm by searching for my own hobbies, my foryou feed has been pretty great. I think probably every now and then it gets stuck in some local optimum, but it's pretty responsive to when you search for a specific niche going forward IME. Ultimately though like other commenters have mentioned, the content can be pretty shallow compared to other media

Speaking as a tiktok-using millennial nerd, it only took about a week or so for my feed to exclusively send me content on D&D, tech advice, science fiction skits, history lessons, and the occasional book review.

The content is there, but sometimes you do have to help the algorithm a little by using the search feature and liking the sort of videos that you actually want to see.