My impression might very well differ from yours, but I'm not reading so much "praise" for the 2.0 and 3.0 and rather things like "At least they had this..." - I recall the grind vividly, and atmas were hell! (I was very much convinced that the atma in western Thanalan just didnt exist)
And I try not to hate on Eureka, but instead try to express my dislike for some fundamental choices both within the content itself and in regards to the relic.
While I cant say anything good about the atmas (except maybe that they looked pretty in my inventory), I will challenge you in regards to the Anemos books, crafted turn ins and light farm.
The anemos books at least required you to do different types of content - I didnt like all of those contents and one could argue that its basically just killing mobs (with the addition that waiting for FATEs wasnt fun - and that person would be correct), but it was always a little bit different. Unless Eureka changes suddenly after Pagos, I havent gotten that feeling there. I'm just killing open world mobs of a certain type or a certain level for hours to eventually have a FATE spawn or my challenge log finished. Or I'm rushing across the map to get from one FATE to the next.
Crafted turn ins are something I'd like to defend from the perspective of a master-crafter, not of the perspective of the person doing the relic-quest. Being a master-crafter though I see how... unimportant that is for the most part. Sure, I'm still making money from selling gear and food and potions, but with the release of new patches, with 24-man and NM-raid-gear I can see my markets shrinking. Most people only gear up one or two, maybe three jobs, so there is no need for the crafted gear. Making the relic-step require crafted goods was really nice for the crafting industry!
Light farming could be argued is the same as in Eureka, except... is it not. The old light farming offered me a variety of content to do so - dungeons, raids, trials, PvP... you name it. Much more options to pick and choose from, while Eureka seems to be just more of the same...
At the same time a lot of those steps helped to get people ro re-run older content - the Stormblood-relic created the problem that in order to obtain it later, they would design some sort of incentive to re-run that content.
I dont hate Eureka, but I think it has an aweful lot of unused potential, has the problem of becoming less and less accessible with time moving forward, is incredibly unfriendly to both solo play and groups of friends who'd like to progress together (and dont want to create a "Eureka-static") and has the relic-weapons only as an "afterthought". While Eureka itself has a story, our wepaons dont (beside Gerolt telling us "Hey, I can make an even more badass sword, if you just collect 400 of those crystals that have a random chance to drop!"). I always liked the stories behind our relic-weapons, even if was only a line or two...
I dont hate Eureka for what it is - I dislike it for what if could have been, if some minor adjustments were made - level-synch, something like the weekly challenge log right at the start (maybe even daily quests!), more exploring (personally I always liked the hidden chests in Diadem, something like that could have worked), some lore for the weapons (writing lore is "cheap" - and we could have discovered old scriptures or something, telling stories of weapons of old that Gerolt could have used as models for our weapons and read to us - could have even re-used names from FFV and based the lore on that!)...
Eureka might be a step in the right direction, but its far from being there yet. At least not as long as people can say "At least I could solo my ARR-relic" and "At least my SB-relic had some lore attached to it!"
I dont believe people mind a grind in general - but Eureka is a pretty bad grind... not in terms of how long it takes or how difficult it is, but of how much of the same it is and specially how restrictive it is in regards to people you can play with.