Eureka is bad, because it encourages the player community to be more toxic. You don't see people starting fights over Verminion or Chocobo racing. There's a difference between optional content that can 'safely' be ignored, and optional content that emotionally manipulates people into thinking 'they have to do it.' And that kind of content is toxic for the community.

Square Enix knows people will go through great lengths to complete their relic. But when those challenges are hidden behind optional content of which people don't like--they'll get resentful that they felt forced to do content they hate to achieve the goal they're after (the relic). It stops becoming about playing for fun and running what you enjoy, but more about wasting your time chasing after a reward, and then being angry and bitter the whole journey. Square-Enix should be responsible for laying down the roadwork for a well-meaning and cooperative community--rather than purposely taking advantage of people's emotional short-comings and pitting them against each other.