Oddly, our losses had one thing in common: they were both Arbor Elf / Utopia Sprawl decks, which seems like really difficult matchups for Mono-White Taxes since our opponents can make so much mana that our Thalia, Guardian of Thraben and Vryn Wingmare aren't all that effective
Two mana for a 2/2 that taps to add a green is already in the realm of playability, while the Fetch Quest adventure provides a potentially game-winning play later
Its much more likely that they are, in fact, competing in the same space
It's such a powerful way to end the threat from an aggressive deck, leaving behind a relevant body to attack back with on the next turn
I hope this helps inform your buying decisions
Being aware of how and when the deck can run into a very rough early game before you sit down to play is something newer players should be made aware of