Well, when they said Diablo-style loot, I guess they really meant it. Launch Diablo 3, that is.
Here is how loot worked on launch Diablo 3: Very few (read none) legendary drops before cap, making gearing and leveling uninteresting. Very few legendaries were actually worth anything or had interesting, build affecting affixes. Stormshield, some Natalya's pieces, a couple of belts and very few rings were useful due to high native stats. Anthem doesn't really have the benefit of set pieces, which Diablo 3 at least included. High variance in random stats while top rolls had underwhelming, samey effects. Straight up useless or bugged affixes that didn't provide any benefits (weapon elemental damage was bugged and it did nothing on any weapon it rolled on. You could roll main stats -dex, str, int- on class specific items that didn't benefit from those rolls -sounds familiar, doesn't it?). Whole weapon classes like two handed swords were completely useless to every single build beause they didn't provide a single unique stat that distinguished them from the rest. The only advantage swords had at some point was Attack Speed. Guess which was the first, only affix Blizzard nerfed before doing any single instance of balancing? LOL. The best ilvl items were behind Acts 3 and 4 on Inferno difficulty. Except, clearing that barrier required some of those items due to the difficulty curve. Beating bosses wouldn't actually yield any significantly better loot than random elite monsters either.
Blizzard actually made this worse by implementing a few changes, the 2 most notable ones were: they increased the penalties for dying/repairing damaged equipment and they added enrage timers that made long, hard fought battles impossible after certain point. They assumed this would discourage people from even trying that content, but the ilvl fence meant that there was an effective cap on the stats that drops could roll in acts 1 and 2, so it was a requirement to leap ahead to make any kind of gearing progress. Due to the lack of endgame specific content (because Blizzard in all their wisdom wanted to push people to run entire acts again instead of doing boss runs) the efficiency of running bosses or particular areas was largely diminished (the whole loot genre is basically time vs reward commitment. Bullet sponges only significantly delay people rushing to the best gear when the best gear can be acquired at a significant rate that doesn't make you feel you wasted your time) and because everyone was undergeared, the most efficient alternative became farming goblins: high hp enemies that dropped considerably more treasure and do no damage. Fun it was not.
People will take the path of least resistance every time if your balance is out of wack and the difficulty peaks and valleys are working against them. I mean, the Diablo team admited they only doubled the damage numbers they've been testing on Inferno because their userbase would find ways to outsmart them, but that lack of testing (plus the presence of the AH which became the single most efficient way to get gear) meant they never really understood the experience their playerbase would have. They patched a few things during the following months, but even adding paragon levels, removing the auction house and reworking a lot of loot affixes and legendaries to have more unique effects was just a band-aid. It took them a whole two years to get the game to a place where people were enjoying the treadmill and loot was actually decent across the board. And this is Blizzard, basically the kings of the genre at that point. (Path of Exile is the new king btw, where they actually learned lessons from Diablo 2 and innovated in other aspects like barter economy).
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And here we are. Making the damn same mistakes Blizzard suffered through in 2012 and basically wrote the book on how to fix them in 2014. They did all the work for you already. How does this happen?