This card gives a creature +0/-9,999 which, unless something very strange has happened, is going to kill pretty much anything
it makes for a more interesting story tapestry, and that seems to be whats happening in MTG
Heartless Hidetsugu does insane amounts of damage, and if you have more life than your opponents the ability will essentially double your lead
The card cant be ignored by combo/storm strategies and it deals damage even if it eats a removal spell
As far as Magic Arena goes, there isn't really a way to get the deck cheaper than eight rares and four mythics since Dorothea, Vengeful Victim, Katilda, Dawnhart Martyr, and Hallowed Haunting are the foundations of the deck, although turning a rare dual land into Evolving Wilds does help with the cost a bit there as well
Its a cheap and efficient way to dig into your deck and manipulate how the next few turns will unfold, and for more convoluted spellslinging strategy, playing cheap spells is the entire strategy