Deep Rock Galactic by Ghost Ship Games, or an early access done right.

Deep Rock Galactic has a simple setting: Four dwarves in a futuristic setting are employed by the Deep Rock Galactic corporation: a mining company that sends its employees in dangerous caves in order to mine rare and precious ores.
But the caves are already inhabited by dangerous bugs that will hunt you.
That is also why you, the four dwarves, each have a respective class (Gunner, Scout, Driller, Engineer) that includes deadly weaponry and useful devices. For example, the Scout has a grappling hook and the Gunner can set up zip lines. Your class has a role and you should do whatever you can so your team survives and complete its mission!
The caves can be dug through with your pickaxes and are mostly destructible. There are several biomes that each have their advantages and downsides (The Glacial strata will occasionally get you frozen, the magma one has pools of molten lava...)

That's it for the summary of the game, but what about it, in the end?

The game is honestly fun. Especially, and that's typical of those kinds of games, when you are playing with friends. The last content update (Nov. 2018) has come with new weapons for everyone, and that M1000 Rifle for the Scout is particularly fun to use!
The game is okay considering its graphics, but it is absolutely not its main argument.
However, the game is in early access, and there is a reason for it. Though the core stems from a good intention done right, this game should be compared to Warframe when it was released in open beta, back in 2013: Fun premiss, but lacking in content. The game IS lacking in content, but that should not be held as a negative point for an early access game that still receives monthly major updates. That is also why I categorise this game as an early access game done right: You can feel that the developers mean right and want to improve their game. They also listen to the community.
However, one could still deplore certain glitches that have been in the game for a long time now. For example, if you remain on the outer part of the drop pod when it leaves the station, you will sometimes spawn underneath it when it lands and be stuck in the map. You will have to leave and rejoin the game.

In the end, on one hand, if you want a fun cooperative game that can and may offer you some challenge, that contains dwarves (Eh, I have heard it was a boon for some), and can become much more, then I highly recommand Deep Rock Galactic to you.
On the other hand, the game can quickly become grindy and repetitive for most people. If that type of things push you away then I do not think that Deep Rock Galactic is a game for you, at least until more content arrives.

To conclude, even though it is somewhat flawed on certain extents, although considerably less than most early access games, the game is good and I personally expect more from it. Ghost Ship Games, you are on the right track, keep it that way!