Every single Lemmy instance could theoretically be doomed to repeat Reddit's path. Including the flagship instance, lemmy.ml. Theoretically.

However, once said instance is going downhill, people would be far less affected. Because only a fraction of the users and communities will be in that instance; most of them will be elsewhere. And since the instances work under the same protocol, it would be way easier to move the info elsewhere too.

And the admins of those instances know it. That discourages them to be abusive towards their own users, because unlike the Reddit admins they can't rely on people coming back.

That's the beauty of the Fediverse. We aren't putting all our eggs inside the same basket, but even then we can make a tasty omelette together with all of them.