Most of the reasons are just the Merfolk are very strong and also that Hakbal of the Surging Soul, the face card, allows you to use the explore mechanic a lot
It's important to keep in mind that colorless mana isnt affected by Hall of Gemstones, so spells that require it will be fine
At the helm is Wilhelt, the Rotcleaver who focuses on the brand new decayed mechanic
Then you must choose one legendary permanent to keep while the rest go to the graveyard
It doesnt end there, though, and if you want to take that position, its probably better to meet other players half-way and build a more casual deck, too
Cage has some flexibility in other matchups, being solid against not only graveyard strategies but also decks utilizing Collected Company and Chord of Calling, like Devoted Druid combo decks