Gen 3 was the first Gen with a coherent theme (disregarding the kemonomimi "gamers") and it's no wonder why this concept cought on not only in hololive, but in other companies as well.
They have a good mix of talents/personalities and it's insane how one Gen contained three of the most successful streamers in hololive.
The only criticism of holo fantasy would be that they're not really close. We have the NoeFure and Pekora/Marine pairings, but very seldom whole Gen collabs, and even those pairings barely exist anymore.