The more it kills, the more powerful it becomesboth as a removal engine and a mana battery
With Nikya, you cant play noncreature spells, but in exchange, your lands tap for double the amount of mana
While the Yellow Cheek Pikachu is the only design you'll find in Unlimited printings, this card will command top dollar in the first edition, as the market price indicates
So while some decks might struggle to produce a big payoff from an X spell, green strategies are often well suited to produce lots of mana in a short amount of time, allowing cards like Invasion of Ikoria to suddenly apply pressure with whatever creature is going to be the best solution to a given situation
I think it's a cool game that requires us to use our intelligence and creativity
Note that a deck need not focus on one archetype