Blizzard wants Diablo 4's outrageous damage numbers to mean something again in Lord of Hatred, so it's letting you crank the difficulty up to near-impossible levels: 'It's going to be really f*cking hard'
The fun of a loot-based action RPG disappears when monsters pop in a single hit and the only thing that goes up are the damage numbers. Right now, you can upgrade your gear all you want in Diablo 4, but the majority of the game doesn't really require it.
This is a problem in a genre where incremental power gains are the carrot on the stick that keeps you chasing after more loot. I tend to quit playing every Diablo 4 season once I'm at the point where I'm only picking up items with slightly higher numbers.