I think the "piloting" ability is mostly (but not entirely) independent of the deck. You can see this most plainly in draft, where everyone is basically playing with a new deck. There are "soft" skills that are contextual and format-dependent, like knowing the cards that you need to play around (white just foretold turn 2, is that a Doomskar? Maybe I shouldn't play a creature this turn, etc). There are "hard" skills that are almost always valid (generally wait until after combat to spend mana, cast instants during your opponent's end step, etc).
But certainly deckbuilding talent is not necessary, because anybody can grab a decklist and head to TCGPlayer.
On that note I'd guess that draft (or sealed) tournaments are the best scenario to measure pure skill using Elo alone, since going into a tournament, everyone has equal chance to open good cards.
[0] Let's be clear, Jeff's deck is bad and he's going to lose a lot, even if he's a time-traveling supercomputer with the diplomatic finesse of Otto von Bismarck.