Treasure Map is a filtering champion
there are many high-Level/Rank/Link Rating Dragon monsters with high ATK (rivalled only by the Machine type) and powerful effects, and several multi-type themes have Dragon monsters as their ace, such as "Judgment Dragon" in "Lightsworn" or "Infernity Doom Dragon" in "Infernity"
It can deal a ton of damage, get rid of whatever your opponent has, and stop whatever your opponent tries to do next, all in one card
If you burn your opponent with Shock first and play Muerra later, Muerra won't be on the board as you spend your fourth mana, and its expend 4 ability won't trigger that turn
Here's a more specific breakdown
With only a fraction of the 180 cards confirmed so far, it seems that Astral Radiance is shaping up to be a top-tier expansion for the Sword & Shield series.