The Diablo games have odd ideas about difficulty. If you played Diablo 3 on normal you probably didn't have to drink a single health potion until the end of act one.
Cranking things up was the way to go, and plenty of people think the same is true of Diablo 4. Hard is the new normal—especially since, as well as offering slightly more of a challenge, it also rewards players with 75% more experience from monster kills and 75% more gold.
It's still not the difficulty you go to if you really want to feel the pain, since there's expert, penitent, and multiple levels of torment above that.
In fact, players starting a brand new character to try out each new season expect to have a smooth introduction even on hard—which is why Diablo 4's seventh season, the Season of Witchcraft, is a bit of a shock.
The story in Season 7 has it that the dangling magical heads on the Tree of Whispers have started to go missing, and we've been recruited by a witch named Gelena to track them down in return for cool witch powers, like the ability to summon exploding frogs.