I am surprised about the lack of alternatives. I grew up during live journal and Myspace days so it felt like new communities were developing all the time. Don't young folks want to rebel against the status quo (including tik tok)?
You couldn't avoid interacting with the rest of the tech stack that provided access to Myspace. You can use TikTok, even have a career on it, and never know a single thing about the web, internet, tech, etc. This is increasingly the normal experience. There's no built in way to learn there's other possibilities unless they happen upon a video about it.
No I think young people want to be a part of the status quo more than anything.
There's a huge moat with getting the critical mass of users to produce/consume content to make everyone follow-on to the platform before your startup cash runs out. That all depends on technical competency to make and keep it smooth, on top of offering enough to creators and advertisers to be competitive.