Platforms can survive as long as they continue to work for, worked by, owned by and controlled by the people.

The biggest example of that is democracy. As long as people have some measure of control over it, democracy will last. But once that control and influence is lost by the people, then it will end.

Reddit was never in the control of the people which is why it will eventually fail and fade away.

The fediverse looks to be in the hands of people right now and it may last. As long as it stays in our control it will last. But once that control is lost to a corporate interest or to a very small group of people, it will be lost.