Almost everyone agrees loot is boring and unrewarding. I think it really boils down to just one design decision. Blizzard made the exact game that Diablo 1 and 2 fans were hoping they wouldn't make. The return to darkness motif played on fans nostalgia for these classic Diablo games, and based on communications from the devs, like these, fans expected MORE than just a return to darkness in the art direction - but were hoping for a full fledged return to form.
Take this comment from one quarterly update for example: "d4 has the art style of D1, with the progression of D2". This gave me hope that D4 would be a return to the franchise roots. However, it's clear after just 120 hours of play time, that D4 doubles down on the design decisions made in D3. Blizzard doubled down on what fans of the classic D1/D2 hated about D3.
Ive played probably over 1,000 hours of D2, roughly 450 in D3, and close to 120 in D4. At this point, I can't really see myself playing anymore D4 or even finishing my battle pass (13 levels left in it). By level 70 the game is an absolutely unrewarding slog, and it feels like work that I don't want to do.
After much consideration I believe I know what happened to put D4 in this state; The most serious problem with d4 is the item scaling system.
In D1/D2 armor/weapons did not scale, but instead would have a fixed armor/weapon damage stat with a top and bottom range. As a player levels more powerful affixes will become available, but the item type (ex: long sword) would always have a fixed base armor or weapon damage. This system results in low level gear potentially being awesome. As an example: At level 40 gear could drop that only requires level 15, because the item base is low tier, but it may roll with the much larger affix boosts available to any level 40 item. Therefore a level 15 item could be viable unreliant on the static damage stat of the weapon/armor itself. Getting all the right rolls to make low level items good even at higher levels happened fairly often, and it's these items that would inspire alt builds or another play through. It is why rares could be best in socket.
In D3, and D4 which uses the same base code - all items were homogenized in the name of balance; they were given roughly the same atk speed, and damage, whether 2 handed or 1 handed, and weapons themselves weren't even used with the attacks - they just increased power and damage reduction - and the attacks themselves were just animations for skills. Because, in D3, skills were modified through gear, and not through the skill tree like D2, gear was made to scale. This way you could use the same skill modifying legendary items at high level as low level.
What ends up happening with this scaling design is that you get stuck in set cookie cutter builds. Because monsters are balanced around the assumption a certain level character will have a certain power - instead of a range of high/low potential. With item scaling and "smart loot" you are guaranteed to always find gear your level. So you increase your power not through finding better higher tier items, but by picking up literally any new drop once you level up. These higher level items are guaranteed to be just a small % increase in stats so that they match the increase in monster power. These small increases in power are not rewarding.
In D3 and D4 all gear is designed to be available to anyone at any particular level, and enemies are balanced around skills that only become viable if you have the necessary, scaling, legendary aspects. In these games you never are looking for actual new gear, just filling your inventory with mostly salvagable and homogenized rares hoping for small increases from level to level.
D2 inspired genre greats such as: Grim Dawn, and Path of Exile, and the non-scaling itemization and balance of those games is so much more rewarding. You actually find new exciting items in those games. They are all about the loot hunt, just as D2 was. D4 is all about the paragon grind, but because of item scaling and gear homogenization there is just no rewarding loot.
D4 does not have the progression of D2, contrary to what the devs said. In d2, you progressed by finding new and rewarding gear tiers, which would require certain attributes to equip. By having attributes as gear prerequisites, players were given multiple paths of progression, and a shiny new piece of armor may not b