Who needs cards when you're using all your mana to protect your Masticore and using it to kill every man your opponent plays
Not only can we immediately upgrade the mana base, but also, now that surveil is an evergreen mechanic, we get more surveil cards all the time (just see the Murders at Karlov Manor surveil lands), which means the deck should continue to improve little by little, set by set
For three mana, you get to search for an instant or sorcery that costs two or fewer mana
A cards rarity is almost irrelevant
Cards like Sun Titan are ideal for this plan, as you can use them to accrue significant value over time through creatures like Eternal Witness, Loyal Retainers, and Wood Elves, fetchlands like Bloodstained Mire, or even previously destroyed mana rocks, so having a big creature or two that can fill this role is very helpful when possible