I'd say it could be described as brutal due to the lack of handholding, so if you die, you lose stuff, and if you died in a bad spot, you're kind of screwed unless you manage to take the stuff back in a smart manner, or just running for it.

But for me the brutality comes from the amount of left clicking on rocks you'll be doing. Pretty much it.

Edit: Plus dealing with bad RNG. That's the second one e.g. barely to basically no crypts found after searching for hours. That type.