You see engagement and/or audience go down if you post less often or don't use the newest feature that platform is pushing.
You find yourself getting trapped into topics or formats because the platform's algorithm has pegged you as belonging in a category.
You find that the platform is exerting too much ownership on your content, perhaps even going so far as to use it to sell itself or to raise its shareholders' profit margins.
You find that increasingly, your ownership of your own creations is being subsumed by the platform's identity. You start getting known as someone from that platform.
You find the platform devalues good conduct and allows abuse and dishonesty in the name of free speech even as voices that need space are edged out by use of aggression and crowd power.