In my opinion Tiktok is a viable replacement for Instagram, a platform that generates on the order of 10B USD revenue a year. They both have pub/sub models where you can follow topics or celebrities or content creators you care about. Instagram is more photo focused and Tiktok is more video focused. The video first format is arguably higher fidelity/more compelling for content consumers.

Yes, people jump from platform to platform. Instagram will not be king forever, but it will be generating massive amounts of money both on the upswing and the downswing.