Earthcraft is not even all that busted anymore. What does it combo with, just
Squirrel Nest? Both are answered by Abrupt Decay, can be pre-emptively discarded or countered, every deck has access to Pithing Needle, other combo decks can achieve their combo faster and just as (if not more) consistently, and there are a variety of control deck answers. If a card like Show and Tell is allowable, and if Entomb + 1-2 mana reanimation spells are allowable, I don't see why a relatively slow combo requiring multiple elements is unsafe. It being Not-Blue is also a factor. This card is arguably just as safe as other weird combo finishers, and it's not like Cephalid Breakfast or Oops All Spells is tearing up the metagame.
As mentioned before, Elves already has access to plenty of mana via 4x Gaea's Cradle and its creatures. So this would really just give a deck like Enchantress an occasional combo win and maybe push it into being a viable Tier 2 metagame deck rather than languishing as a Tier 3+ pile that's been outclassed for the last several years.
Alternatively, I *guess* some decks running green might add it somewhere to their 75 as alternative win condition, but then this still isn't much more busted than something like
Helm of Obedience + Leyline of the Void or Rest in Peace. Less mana per combo element (which are individually next-to-worthless unlike Rest in Peace), but provides a slightly more fragile setup that is also an Abrupt Decay target. The Enlightened Tutor argument didn't apply to these elements either.
Existing decks already run plenty of answers (Wear // Tear, Golgari Charm, etc.) so even if it were a legitimate threat it's not as if answers are lacking. And let's say that somehow Enchantress were to actually become a legitimate, Tier 1 deck requiring actual consideration for sideboarding: cards like
Back to Nature and
Reverent Silence exist. And personally, I think it'd be cool to have another underdog fringe strategy that doesn't win via 'normal' creature combat become a viable metagame choice (similar to decks like Lands, MUD, etc.)
If stuff like Land Tax and Black Vise can be re-evaluated, Earthcraft deserves the same. Legacy is a very different format nowadays.
tl;dr unban Earthcraft already, it being on the banned list still is embarrassing.