I think one of the differences (at least when I watched anime way back in the early 00s) is that anime relies on a whole different set of tropes from Western movies and cartoons, and those tropes are unfamiliar (or were, anyway) to Western audiences.
When I started watching anime, it was hugely refreshing to be caught by surprise by plot twists and dialogue, and to see characters & themes that felt totally original.
But then you watch more anime, and realize…oh, they weren’t unique, they were totally stereotypical. You just didn’t know the stereotypes they were based on.
And before long you can see plot twists a mile away, the characters are predictable, and you can describe a new series as “basically X, but with some Y and monsters instead of robots”.
It’s the false promise of that initial discovery that makes the eventual realization that much more disappointing.