I actually disagree with this. AoS is anything but generic. It's what I would call cosmic fantasy, and the models have a look all their own. The lore is completely batshit, but hardly unoriginal. Yeah, the Stormcasts are the very definition of no personality, but to balance it out we have steampunk dwarves, elf-medusa hybrids, and an entire faction of tree people.
Whether it's actually good is another thing, and one I'd say isn't even up for debate. The AoS setting is incredibly poorly thought out. It's next to impossible to even define where it takes place, since it has no concrete places or connections. It's less like a painting on a canvas and more like random splotches of paint splattered across a forest. "There's umm, like these mini-dimensions that like, float in space and, umm, you like... travel through these gates to move between them and... uhh..." It removes any sort of concreteness or consequence from the setting, since there's no established locations or maps, but just disconnected individual blips instead. No definition of what the whole looks like, how anything is located in relation to anything else, no distances or borders. I typed "Age of Sigmar map" into google image search, and all it shows is random nonsensical maps where the landmass doesn't even have proper borders.