Simply put, the deathtouch ability means that any amount of damage that card deals to another creature is enough to kill it no matter what the other creatures toughness is
The problem with Geminis in general is that every monster over Level 5 is a potential brick that you can only really get around by drawing into another copy of your Field Spell
Having a single one in hand as the battle begins can lead to a quick and devastating early-game strategy
The man selling them insisted that they were indeed found in a dumpster ("I've made over $60,000 off these f****** Yu-Gi-Oh cards out of the trash," he claimed on a public Facebook post that can still be found), and began firing off rather uncourteous replies to those who questioned him in the comments
In addition, it adds new mechanics that set up "some intriguing design space for future expansions." It also feels easier to find in stock than other expansions
Although it has its downside, its one of the cheaper ways to end the turn