I’d argue that what you're experiencing isn't the Network Effect anymore, but rather Vendor Lock-in.

The Network Effect implies the platform gets better for you as more people join. If they are deleting your content, the network is no longer serving you—it’s just holding you hostage. This is enshitification as it best. (this ironie with a cory doctorow link)

At this stage, it’s just a walled garden. Staying because 'everyone is here' while being silenced is learned helplessness.

You're voluntarily staying in a walled garden that refuses to let you speak.

But: The door is wide open, you can go.

I agree with you, but perhaps walled garden and network effects are not mutually exclusive. I.e. if I leave the garden, I'm losing value of being able to reach many people I care about.