There's an unofficial translation of an interview about the development of Eureka floating around on Reddit (not mine): https://docs.google.com/document/d/1...6GzIzadxA/edit

Most interesting bit to me is it looks like Eureka is more popular than they thought it would be:

Y: As Mr. Nakagawa said, there were far more adventurers delved into Anemos than expected. We initially expected the Eureka playerbase to be mostly limited to people who are comfortable with the attribute of repetition or MMO players who are active communications. Pagos was basically the content that aimed this narrow “elite” player-base to go deeper. It was our fault to not expect that there would be much more casual players along as well.
I was under the impression that Eureka was meant to be a core feature of Stormblood but it looks like it was always intended as a niche activity. It performing above expectations might also explain why we didn't get official responses to the complaint/criticism threads.

Edit: This is somewhat off topic but I put it here since it's the most recent Eureka thread I saw.