Tier 1
TPC Comments
Shaddoll boasts a broken Skill that generates a lot of card advantage out of thin air, a floodgate in Loading... , and the ability to play Loading... (which wins games on its own). Shaddoll checks a lot of boxes that make it the best deck to play in the upcoming WCQ.
Shaddoll is the current driver of the format: there's a lot of strategies and techs to utilize on top of the suffocating Loading... floodgate, making it the strongest deck in the meta. Shaddoll has a good matchup against most decks, even if it has a problem dealing with Utopia's board going second (but thanks to the existence of Loading... , you won't have to worry about it as much). As such, the deck has more than justified its position at the top of the Tier List.
Shaddoll has a very strong Skill that gives it absurd consistency while still allowing the ability to use Loading... (which is very strong in the meta). This allows it to use the most of its engine and create insurmountable advantage, making it the strongest deck in today's meta.
Tier 2
TPC Comments
Utopia is currently Shaddoll's best rival. Having access to a searchable omni-negate in Loading... and several Monster Effect negates in Loading... and Loading... makes its Turn 1 board very strong. Going second into Shaddoll, it can easily beat Loading... since ZEXAL II – Power the Future generates a free Loading... and Loading... . They also play Loading... for Loading... and even Loading... (since it doesn't need its Normal Summon). For these reasons, Utopia is a contender in the meta.
Since Utopia doesn't have a bad matchup against Shadoll and has the ability to do well against other decks (between its near-unbreakable Turn 1 and Turn 2 techs), Utopia seems to be the second-best deck of the format.