Destiny and Destiny 2 does have legitimate grinding weapons and armor (aka: Iron Banner ornaments, Legend of Acrius, Mida, etc.). Grinding (in gaming) is the process of repeating a specific action/scenario over again constantly to gain experience/items/meet requirements in a game. These grinding activities do create a cause and effect in a good way. Kill 100 enemies with a specific weapon to gain a better weapon? Good use of grinding.
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Now, luck based items are another thing. Like in the Dark Souls games, items can be both bought and earned through enemy drops. Here’s the thing now, you are not guaranteed a specific item you are searching for, even if you repeat the same scenario/action again and again. Luck drops are not usually good things to fully implement into a game because it’s an artificial grind. You can spend 5 weeks going after one item and still not be any closer to receiving it due to luck.
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People like putting in the time IF it has a reward worthy of it. Work 40 hours a week and expect to be paid a specific amount poor hour. Or, work 40 hours and be paid either next to nothing to more than what you normally get paid.