Niether was Ultimate yet look at the reception that piece of content got from the community overall. Even those who didn't run it noted how well made it was especially considering it was just re-using past pieces of content. Just because it's not meant for everyone does not mean its free from criticism especially when its a piece of content that is not only worse than its original predecessor, Diadem, but somehow ignored all feedback the players gave about its first segment. It's already worse than Diadem because it cut out the potential pull for DoH/L that Diadem had. Even worse for content that is heavily focused on Group Play its very punishing on newer players due to the 1-2+ Level differences leading to massive xp loss for all players which further alienated players and essentially set this content up for death once Stormblood ends.
The only difference between Eureka and the Overworld at this point are the generic mobs being HP sponges and having harder autoattacks. Were this style of content really desired and had a following in the playerbase Yoshida could have easily just buffed overworld mobs and put the basic chaining mechanic into it so you can level off it because at the end of the day thats all the Elemental Level is. A system put into place to extend the grind without adding any interesting mechanics. 1.0 Beastcamp Leveling was more fun than Eureka because at the very least you'd be farming Tapers and Feathers for Ifrit/Garuda alongside having a slower combat system, while not as slow as XI, that allowed some proper communication between players. And honestly Pagos has been probably the most socially dead scene I ever scene when you compare how active Anemos /shout chat was. Even sadder when a piece of content has to tout the fact that its very social when an MMO by nature should be a Social game.
This is a grind for the sake of a grind and has essentially killed of all non-Eureka content faster than ever since the Relic is no longer sustaining past pieces of content for progression. So now you're stuck with an expansion where a majority of the population has given up on what was touted as the crowning jewel of Stormblood, people getting bored or ignoring old content cause it offers nothing and the raid tier iLvl reset finally catching up to SE. At least for the Zodiacs and Anima you could go back and benefit from any content you do when it doesn't ask for a specific duty. Plain and simple the concept of Eureka failed to iterate on Diadem and even itself (Anemos), failed to keep the population happy with content and managed to speed up the rate old content dies off.