People were mostly picking aliens as an exploit, it goes without saying that wasn't going to last forever.
It was not an exploit but major game balancing faults from the game designers.
For space but als ground, if you want to be competetive in PvP, you have to have traits like accurate, elusive, warp theorist and so on. It is not the player's fault, that some traits are just much superior to others.
My "Alien" in fact looks like an Klingon, because Klingons can not select elusive as space trait, so I had to choose an Alien. However, I rather would like to pick Klingon as race, but was - from the point of game design - not allowed to.