I realize that, like any Pokémon with the correct set up, it can destroy teams with its high special attack and nasty plot and spikes and good coverage etc.
Yes, not a lot would like taking a hit from it, so you can't just switch in anything. But using that argument, not a lot likes taking a hit from Pheromosa (relevant because it was legal when SM came out), Xurkitree (tail glow or not), Kartana (swords dance or not), Hoopa, Landorus, Buzzwole, Zygarde, Tapu Lele, Tapu Koko, Tapu Bulu, A-Marowak, Greninja (battle bond or protean), Heatran, Excadrill, swords dance Mimikyu, tail glow Manaphy, Tyranitar, Magnezone, pretty much any offensive Mega Pokémon like Charizard, Beedrill, Lopunny, Alakazam, Metagross, Garchomp, Medicham, Mawile, Pinsir, Scizor, Gyarados, Heracross, Swampert, etc etc. Hell, name me one thing that enjoys switching in to a Mega Pidgeot's Hurricane? At least Dark Pulse doesn't confuse you
When you compare Darkrai to that list of offensive threats... it just feels meh