Agreed, there's a reason that the AoS youtube lore scene just doesnt work as well as the 40k youtube lore, many things in 40k are compelling for their insanity and this hooks people very easily, most factions have something fascinating about them.
In AoS, if I wanted to create that 'Pull' you are talking about I would probably start by making the eternals have something deeply f**ked up about them. For example there could be a severe flaw for some of the eternals exacerbated through dying repeatedly where they start drinking the souls of innocent people. There could be some messed up dynamic where the public are giving a part or all of their soul to the eternal because of their belief and devotion to them, not knowing the eternal is descending into madness. At at a certain point the eternal devolves into being a feral beast and ends up ruling over a backwoods feudal town clad in dark clouds, slowly devouring the souls of the inhabitants and slowly becoming physically monstrous in some way.
Then a secret cabal of eternals that not even other eternals know about come in and exterminate the feral eternal and then cover up what happened by slaughtering the surviving town inhabitants and all in the surrounding area, tens of thousands killed to hide what is happening to just one eternal. The secret cabal believe what they are doing is a necessary evil as having the people turn against the eternals would invite chaos. Then when you start seeing subtle hints of this feral-ness and hunger appearing in a big important character, general etc, its like an 'oh sh*t' moment, are they going to turn too? Is this terrifying flaw in more than just a few of the eternals? What happens if a feral eternal is left to feast and change until it reaches its final form?
I could probably hook a newbie with something like that a lot more easily than they just become more godly and inhuman as they die more, it feels more juicy.
Nagash is a great arch-necromancer design visually, and I feel like he could make fascinating antagonist in a video game where he is animated and voiced. (Maybe that game Frontier is making) but I feel if I'm telling someone about him I'm missing a hook, or rather something he accomplished that makes you go 'woah'. I'd have him discover a continent in the mortal realms which is inhabited by a billion unknowing people. He then turns all of those people to undead and then forms them all together creating some kind of named horrifying amalgamation monster out of a billion bodies (or maybe just millions) , something that flows or strides across the land, or maybe a great floating city made of death. The scale of it is the conceptually compelling part here, you get the 'oh this necromancer is so terrifying that he can turn a billion innocent people into this single mind bendingly horrifying creature' kind of deal.
The Skaven are probably the faction with the most lore 'juice' in AoS honestly, they are easiest to explain to someone in a sentence that makes them want to know more and they feel the most unique to warhammer. "Crazy rats that all believe they are the chosen one and build insane machines that blow up killing their side half the time, they are also innumerable." or "Crazy fantasy rat people who can build nuclear bombs" referencing the pseudo-nuke they made in the end times.
Making things instantly compelling and have 'Pull' is hard. Making fantasy factions that stand out from generic fantasy is hard too.