Lemmy is great but it does not hit the spot for a large-scale consumer social network because that's just not the philosophy (It also lacks the unified identity because of its greatest feature: federation)
People are not searching for an aggregator of small forums of friendly tech people, they want to be part of the next big thing.
If you work on apps as a front-end, you probably understand that Lemmy requires too much hassle to get started with UX-wise.
It's engineered for a niche, and it's perfect to me but obscure for the majority of people who were trained to use the same UX for years and years.
No algorithm, no feeling of fame, rarely drama, content takes some time to be updated. Those are features to me but hindrance for large-scale adoption I believe.