In the past I used IG to interact with people from niche communities (primarily aquarium related) but I left both because it was acquired by Facebook and I was seeing the huge increase of ads and sponsored posts/accounts as you describe.

From what I've seen of tik tok it seems it's mostly young kids and teenagers lip syncing music, dancing, and doing comedy sketches.

Are there communities in tik tok where people from niche hobbies can share information and communicate? If I could join and find other serious aquarium hobbyists, for example, I may actually consider giving tik tok a try but I was under the impression that doesn't really exist or fit the use case for the app