I’ve played a fair amount of Diablo IV, and all of it’s predecessors except Immortal, and watched a number of opinion and reaction videos from various content creators. It feels like most people talk about the mechanics that are wrong without addressing what’s really happening.
First, this game has wonderful class identity, each of them look great with interesting and varied skills. However, actual gameplay is monotone, you stack crit, main stat, crit damage, and then combat is apply vulnerable, maybe stack a few conditions to proc equipment effects, and then do your main skill. This is followed by recouping your resource and then wash, rinse, and repeat. If the combat loop were different for various builds or classes this feeling of monotony could be alleviated, and it seems the devs are aware of this in patch 1.1 and in the campfire chat with nerfs to vulnerable damage, main stat on equipment, and crit damage multipliers. Hopefully this awareness leads to more varied and unique playstyles.
Second, many creators talk about items being bad, and then cite affix pools that are too large, item level scaling, and other concerns. In my opinion these all boil down to lack of item identity. I am rarely looking for an easily identifiable item, such as a unique, and often find myself reading through an inventory of items and affixes looking for the right stats for a character or build. In D3 I would simply look for an ancient, primal ancient, or unique piece of armor. In D2 it was a unique shako, a unique gilded shield, or a high rune. Items in D4 are rarely iconic and often just a wall of text to sift through in the hopes one has the right stats in conjunction with each other, or a good roll on a legendary that you can extract.
Finally, and this is more subjective, there is little creativity. In any arpg you can customize a character to your playstyle, perhaps with gear or a suboptimal build. But where are the melee sorcs, the singer barbs, from D1 the warriors that are still casting spells, and other unique builds. In this game you can barely kite if that’s your preferred way to play due to the camera distance.
There are a lot of things to like about this game, and the developers did a wonderful job of cherry picking the best attributes from previous diablos to create an interesting, and mostly fun, play experience. Some of the pieces still feel like they’re missing though, and hopefully they get put into place sooner rather than later.