There is plenty of "grind" in D2, most of which is a time spent, reward gained. Even if those rewards are lackluster.
Cores are an issue because they affect player choice, maybe not YOUR choice, but they do affect the choice for a lot of people.
And that's it. They are a pointless barrier to choice, nothing more.
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What must be removed is Fabled/Legend from all crucible weapons so that all players can play with what they want, when and how they want.