I don't know why they would quit. Unless you're really good, you don't have to much pressure on your shoulders and you can play for the fun of the game rather than to get an invite (That you're expected to get) like in seniors.
I was on PTCGO with quad Mewtwo/Meloetta/Ho-Oh EX and beat it. I think you need an answer to mewtwo, because it steamrolls you. Also, Big Basics is a hard matchup so you might want to consider Mewtwo or Tornadus EX to hit them hard.