I personally like Eureka, Diadem I liked the concept but the problem seems to be..as long as we're stuck with 2.x formula, no matter what they come up with is gonna be shit because of the core systems they don't want to change. Like "grinding" works well, it doesn't work with XIV's systems. Eureka coulda easily been Abyssea, which while I hate it for what it did to XI (obsoleted stuff in way too quick a fashion) it was still well structured compared to most of the stuff XIV has put out lol. It's just weird how while I get "XIV IS NOT FFXI OMFGGTFO!!" that people love to say in OF/Reddit, just a bit funny that XI, for as old as it is, still has more structure and better progression flow. Every MMO had its growing pains and tough spots (like WoTG for example ignoring the FFXIV Development time hindering that expansion) but XIV seems to constantly be in that "growing pains" stage that people who don't do the game's content continue to eat up.
Like we do get actual progression every 6 months then eventually an expansion to reset us to 0, but if this was any other game..players wouldn't stand for that and the MMO would have died ages ago. I think even Yoshida commented on that in a recent interview (regarding MMOs rarely lasting.)
It's weird how we get less content for "better/unique content!" every expansion so I'm betting 5.0 we'll lose primals (CUZ GARLEANS DON'T HAVE THEM! - Lore Shield) for "unique content" that's gonna be a 4th iteration of Diadem.