They do nothing against mono color decks unless Richard is building the manabase, but against multicolor decks they can often be free wins and are definitely the highest win % cards for their mana values
I also like the way it incorporates its preevolutions, with Ralts, Kirlia, and regular Gardevoir
Wizards has somewhat addressed this issue with its Universes Within versions of the cards
You'll also get the Gilded Lotus promo if you purchase one of two bundles, one in English or one in Japanese, for $199.99
Its hard to say exactly why this card is performing so well, but the most likely answer is how rare it is to see a Shiny Pikachu
At the beginning of the chosen players upkeep, this artifact deals X damage to that player, where X is the number of cards in their hand minus 4