Blue can draw the most, sure, but it also has many, many redundant effects and cheap options on the curve that can do other things
Series 1 includes a special booster pack that gives you three of nine illustration rare-style promo cards, all centered on first partner starters from Kanto, Sinnoh, and Alola
Like the original Pokmon ex and Pokmon-GX, Pokmon ex evolve from non-Rule Box Pokmon
The broader landscape around the Giratina VSTAR has fed into its power too, with Comfey and its Flower Selecting ability, Cramorant and its Lost Provisions ability, and Sableye with its Lost Mine attack all fitting together neatly
Ardenn is infamous as an equipment Commander