On Paper Shortly after rotation, most of the popular cards in Standard would have already started to see their value go down
Fetch Lands Mana fixing alone is far from broken, but fetch lands do so much more
They are Vrondiss, Rage of Ancients (a Dragonborn Barbarian, leading the red/green Draconic Rage deck), Prosper, Tome-Bound (a Tiefling Warlock, helming the red/black Planar Portal deck), Sefris of the Hidden Ways (a Genasi Wizard, leading the White/Blue/Black Dungeons of Death deck), and, finally, Galea, Kindler of Hope (a Half-Elf Paladin, topping the White/Blue/Green Aura of Courage deck)
If Explorer's Cache isn't on the battlefield as its activated ability resolves, you can't remove a +1/+1 counter from it, so you won't put a +1/+1 counter on the target creature