Eureka objectively took much more resources than Ultimate and is considered casual content (whether or not it managed to do that is another debate I don't mean to go into). Even beginning to compare the amount of resources needed to make Ultimate vs. what it took to make Eureka is an insult to the development process. Eureka required designing of a HUGE new mode, all the cinematics and quests, a billion enemies, NMs, achievements, much more gearsets and weapons, about a dozen NPCs that needed to be put all over the place, and that in turn also means a lot more things that need to be tuned and maintained...
Development is a zero sum game. Every piece of content developed means something else was either pushed back or cancelled outright. But if you think Ultimate is the main offender in why we're been getting less content across the board, you're very likely mistaken.
