These types of spells tended to be cheap, to maximize the amount of times they can be used for "free." Early plotting is all well and good, but at some point you have to actually make the cards with the mechanic
Beyond card images, there's a world of interesting AI/ML applications with Magic, like what others have worked on for drafting, deck optimization, and game play
You need to tap Marshland Bloodcaster and spend two mana to get the ability to work, so you'll have to wait a turn and ensure you have enough life to pay when you cast that next spell
Split Up Split Up is a 3-mana white sweeper, and one that you can use to your advantage, especially with tap and untap effects
Wizards is definitely missing out on a decent chunk of potential revenue by not making gift cards available
On the other hand, their weakness stems mostly from a lack of permanent removal once a threats actually on the board