RKS System is an objectively bad ability, because from a programming standpoint it has no reason to be an ability at all, it could've just been part of the effect of the Memory items.
Is Pikachu's ability "can receive the effect of a Light Ball"? No, it's Static or Lightning Rod.
Is Chansey's ability "can receive the effect of a Lucky Punch"? No, it's Natural Cure or Serene Grace or Healer.
Is Ditto's ability "can receive the effect of a Metal Powder or Quick Powder"? No, it's Limber or Imposter.
Is Cubone and Marowak's ability "can receive the effect of a Thick Club"? No, it's Rock Head or Lightning Rod or Cursed Body or Battle Armor.
Is Clamperl's ability "can receive the effect of a Deep Sea Scale or Deep Sea Tooth"? No, it's Shell Armor or Rattled.
Is Farfetch'd's ability "can receive the effect of a Stick"?, No, it's Keen Eye or Inner Focus or Defiant.
Is Genesect's ability "can receive the effect of any Drive item"?, No, it's Download.
But for some reason, Game Freak decided that Memory items aren't simply items that affect Silvally.
I guess they really wanted Silvally to lose the effect of a Memory item when hit by Gastro Acid and other specific situations.