Right now everything they're doing is far better than the tired and useless 2 dungeon 1 "raid" formula they had. It remains to be seen if people end up continuing to enjoy Ultimate in a couple weeks once clears start becoming regular but so far most of the hardcore players I know think its fine. For anyone that isn't a casual, once you've played about a year you have literally nothing to do in this game except log in for raid, do some crafting and go in and one-shot everything in the current tier. Progression is what drives players with a raiding mentality and if they have 6 months between tiers with roughly 5 of those months being filled with casual sleep inducing content these players don't really have much incentive to remain subbed or log in except for their weekly clear. Having something like Ultimate that can't be solved in a day on the same 6 month odd patch schedule along with the casual content fills in the gap where nothing is happening, making them stay subbed longer.
I personally think Eureka is going to be stupid and quite useless because I have no faith in them doing "instanced" content zones like that thanks to Diadem. The relics, while nice looking, were just absurd grinds for a weapon that's only good at the end of the expansion when it doesn't matter anymore. Now if only they could put actual effort into events and stop making us do stupid FATEs.