Addendum: To be clear why it doesn't have algorithms is because of the previous mentioned points and privacy.

There have been many who have tried to add such features and always we told them we didn't want something which we cannot explicitly opt-into because many don't want to be searchable due to harrasment etc.

Depends what you mean by success I suppose.

Mastodon is still going strong despite these supposed inconveniences, so I wouldn't call it a failure exactly.