This is a two folded issue. On the one side there is the loot itself. On the other side there are the challenges that the items are meant to help you overcome.
I’ll start with the latter: Before you reach empowered monoliths you just breeze through everything except for the bosses. It doesn’t really matter what kind of gear you have as long as you have enough resistances to not get randomly one shot. You could argue that is a good thing because you get to reach late game faster, right? Well it also means that nothing is a challenge until you have reached late game after a grind of 30-40 hours. And these first 30-40 hours (which is more than the game time of many other games) you just run through the campaign and the timelines, hit two buttons and evaporate everything. An easy fix for this would be difficulty settings that allow you to get on a higher difficulty in exchange for higher rewards in xp and loot. That also makes items more important because better gear allows you to run a higher difficulty thereby gaining higher rewards and so on. That means you care more about your gear because the difference in your gear actually makes a difference in your gameplay. And you could be even faster on your way to late game.
The main issue are the loot tables themselves. There are no real game changers, no items that feel meaningful and get you motivated to grind for them. There are certain affixes that you want. But what kind of helmet or chest they are on doesn’t really matter. For example I play a Bladedancer that relies on a combo of Synchronized Strikes and Shadow Cascade. I look for increased melee or physical damage, increased damage when wielding sword/dagger and increased damage for skills used by shadows. There is plenty of loot to sift through for these affixes and I can set up my loot filters to highlight them. But there is not a single peace of gear that feels like it is meant for me. There is no “Blade of Shadow Dancing” that increases the efficiency of Shadow Cascade in a way normal affixes can’t. Yes there are a couple of unique and set items that do this here and there for a few select skills (but neither for Shadow Cascade nor for Synchronized Strike) and even then they don’t feel that impactful. You might argue that’s a good thing because builds don’t have to rely on items to work and stay more open that way so that people can be more creative. But it also means that loot is ultimately uninteresting because it is just a pile of random affixes and does not feel very rewarding. I never got the feeling “oh wow, look at that, that is such a sweet item for my build!” it was always just a slight increase over the item I wore before in the same slot, a slow but steady improvement of a few % here and there. It never felt really rewarding to me. An easy way to solve this would be to create items that specifically strengthen the skills. There are 5 characters with 22 skills each, so 110 items. Seems doable to me. If you feel like this would tighten up builds too much in a certain direction you could launch multiple items for all skills or even better: implement items for select specializations. For example my bladedancer would happily go hunt down every last Void Spawn in Eterra for a dagger that augmented Dark Allies so that Synchronized Strike would spawn not 2 but 4 additional allies or an amulet that prevented Dark Allies to increase Mana Cost. People could still be just as creative and create their own sets of gear that complemented their skill specializations.