If your opponent is playing a combo deck or one that relies on specific spells you can cut their access to these cards off
Toph, the First Metalbender Landfall is one of Magic's most powerful mechanics, one that offers tokens and card advantage and damage and more just for taking the most basic game action
Feldon of the Third Path is great recursion
Yes, theres a scenario where you can play a bunch of items early on and Shift the new Belle Mechanic Extraordinaire ahead of curve to get an early 7/7 body that quests for three lore with upside, but youre jumping through so many hoops to make that happen
Monocolor (in WUBRG ordermeaning white / blue / black / red / green and pronounced "wooberg" in R&D speak) comes before multicolor which comes before split cards which comes before artifacts which come before land
This one can be wonderful for sneaking encoded creatures through, but with Dimir and Orzhov players out there there will be black creatures all over the place