I completely reject the notion that the mainstream success of the fediverse will be the death of the fediverse, what are your reasons for believing that?
Enshittification happens to monetized platforms because they tried to capture as many users as possible and then profit off of them, lemmy instances show no profit motive, and are volunteer run. There isn’t a route to enshittification with federation, because even if YOUR instance enshittifies, there’s still many others that will not, and due to federation, you won’t miss out on any content (as long as your instance doesn’t defed), so it won’t matter.
I also believe the issues you call out, aside from algorithmically driven content, will be solved eventually, as mod tools improve, there will be less of a need for defederation.
Even algorithmically driven content is partially solved by “hot” and “best” being improved, it’s just not personalized.
With the rate of lemmy development being as rapid as it is, these things will eventually be solved, but that takes a lot of time. Lemmy is still barely even beta.