Sleeves offer several advantages: Protection from Wear and Tear : Sleeves shield cards from handling, reducing the risk of surface damage, scratches, and scuffs
Its attached spell is Swords to Plowshares, which, for one white mana, lets you exile a target creature while its controller gains life equal to its power
This is a reprint, and it was pretty nice in Limited last time
Unless you can pick it off with an exile spell, it's trivial to return it to hand essentially forever for the Zombies player, and it keeps the absolute worst of the worst coming back to shamble on for more brains
Wall of Runes
We've seen abilities like it before on cards like Gnarlid Colony, but having it as an enchantment that also gives the counters needed to enable it push it up to a potential green stample for a good while to come