I've played Last Epoch for ~250 hours (and counting) over the last year since I bought it, so I'll give a mini-review here. The TL;DR is that it feels like a brilliant middle ground between Path Of Exile and Diablo - it has depth and complexity but doesn't have the brutal learning curve that Path Of Exile does. It doesn't have the content variety that Path Of Exile has, but it's also an early access game right now so that's expected. It's a great foundation, their patches have been substantial, their communications tend to feel good, and I feel like they're a good development studio. A lot of the developer insights make it feel like they take very good approaches to problem-solving, too.
The combat feels absolutely fantastic. The animations are smooth and feel modern. It can feel a little "floaty" for some people, but personally I have no issues with the way it feels. It's paced in such a way that fighting regular enemies still feels engaging (unlike Path Of Exile's zoom- and dopamine-fest) but isn't a slog, and more powerful enemies can put up really good satisfying fights. There's a good variety of skills and the way you modify them with the skill tree system can change them significantly. The build depth isn't quite as crazy as Path Of Exile's, but considering most POE players just follow build guides rather than taking their own builds, I'd say that won't matter for most people. And for people who do like creating their own builds from scratch - which I do - there's still plenty of depth to Last Epoch's system.
It's very realistic (and encouraged) for new players to experiment and create their own builds. Respeccing is pretty simple, and the skill systems are simple enough that new players can work it out for themselves, but there are also some interesting combinations and min-maxy things for more advanced players can figure out and build around. Each skill has its own skill tree, and while the trees aren't super complex, there's a good variety of ways to modify each skill. Some of the skills also have interactions with other skills - for instance, Teleport has a modifier that means your next skill has no mana cost; Meteor has one where your Fireball has reduced mana cost for a few seconds after casting it. You can chain that into a skill rotation: Teleport > Meteor (which normally has a high mana cost) > Fireball spam and suddenly you're going to have a much better time with mana sustain, but perhaps need to work out a way to deal with the fact that your movement skill is being used offensively and won't be available for dodging. So the game sort of gently hints at some skill combos like that, but they never feel forced and you still feel smart when you put it all together yourself.
The loot system is good. It has the single best crafting system I've seen in any ARPG, and crafting is absolutely worth your time and a necessity if you're pushing your build as far as it goes. But you need good starting items to work with - you can't just take a terrible item and craft it into something amazing. Crafting lets you upgrade the tiers of modifiers, add new mods if there's space, and sometimes modify items in slightly more spicy ways if you're feeling brave. But items have a "crafting potential" which depletes as you craft on them, so looting items is important.
The legendary item system is also very good. Unique items have their usual fixed stats, but they can have something called "legendary potential", which rolls between 0 and 4. Legendary potential does nothing by itself, but it allows you to combine a purple-tier item with your unique item; the amount of legendary potential you have dictates the number of mods from your purple item that will be randomly added to your unique item. Non-unique items can have 4 modifiers, so being able to create legendary items with the unique stats and powerful regular item stats is a really good end-game chase.
Most unique items are target farmable in the end-game. That's not to say you can get them immediately, but you can target "unique rings" as a reward, for instance, or target a specific boss that can have a chance to drop the item you're looking for. So overall, I think it's a good item system!
I think they've taken a very good approach to problem-solving - their upcoming trade system, for instance, looks (on paper) like it'll fix the biggest issues with Path Of Exile's trade system and Diablo 3's auction house, while also having the benefits of both and while giving players an avenue to progress without engaging with trade at all. (Basically, players join either the trading guild or the "solo" guild. Traders can trade, solo players get a boost to their loot and can target farm things more easily. People can trade with their party/friends separately from this trading system so the whole guild system doesn't matter for co-op play.) It's smart, and that kind of thinking can be seen across multiple systems in the game.