I'm not so sure.
A deck is something you have. A build order, or a chess opening, is something you _know_ and therefore more or less what I'd be comfortable calling skill.
A deck is something you have. A build order, or a chess opening, is something you _know_ and therefore more or less what I'd be comfortable calling skill.
[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.
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.
Top tier commander decks can easily cost over $10,000 I suspect the vast majority of players do not have access to them.
I think perhaps we could agree on an intermediate claim that Elo could work amongst the pool of players that can build any deck they want, which is a big pool for MTGA, and definitely a smaller pool for physical Standard, and probably very small for Commander.
I wonder if you could decompose the score by playing some games with a fixed deck too? Eg Arena challenges. How much of your overall Elo is just picking the right deck for the local meta, vs raw quality of plays?