So its entire story is basically a bunch of easter eggs?
Not necessarily the main story but most of the best lore is. The main story is fairly straightforward and there's enough dialog there to give you context of what you're doing, your overall objective to become Elden lord, etc.
But if you aren't reading item descriptions or paying attention to what NPC's are saying, the game will just seem like you're playing on a massive map with a variety of creatures and bosses, and everything in the world is fukked up for no reason
Every single type of enemy is placed in specific areas and often have some kind of relation/interaction with other creatures/enemies in the game. Same with all of the items. The attention to detail is insane once you dive into it. There are various historical conflicts that have shaped things, multiple gods essentially fighting for control over The Lands Between, history of the demigods, tarnished and their interactions, etc. All kinds of shyt that can be easily missed by most players even if you beat the game
Fromsoft's story telling definitely isn't the most straightforward or accessible, but you can't have dozens of YouTube channels pumping out hundreds of hours of lore videos to this day if there's no story or characters to talk about
IMO the lore hunting and theory crafting is what helped give the game even more legs/longevity because there are whole communities online who still discuss and debate this shyt daily