Energy Flux can run afoul of some of your own artifact threats, but is so potentially devastating against very heavy artifact threats that this may often be worth it
My line of thought back then was its better to have a card in hand I want to cast, than have a creature or land Im not currently using, and while weve seen similar effects printed since then, most of those will be two mana or more (outside of Village Rites)
People are most excited about this guy because of its ability to be protected from both Swords to Plowshares and Oko, Thief of Crowns against Miracles
Beyond just being rare, thanks in part to the limited-run printing of Secret Lair drops, and their Bonus Cards, Mana Vault is insanely strong
Build within Sets 9-13
Instead, he'll be in the back, happily running the casino that is your deck