Skill is something anyone can acquire with enough motivation and practice.
A good player — in the context of a social game in the MMORPG genre — is someone who respects other people's time, effort and feelings. Many would say that respect is a two-way street but, in truth, it begins with you. If you don't begin by showing respect, you'll get none in return.
Everything else follows.
If you respect someone else's time, you'll understand the need to make sure you're doing your best, learning the ropes, and practising to be a better player.
If you respect someone else's effort, you'll understand the need for encouragement, as well as the need for tact when giving advice.
If you respect someone else's feelings, you'll naturally watch your language, lest you offend others without intending to.
In a single-player game where all that matters if you, none of the above matters. A good player is then all about your skill in getting whatever you want out of the game.
But in a game like FFXIV, where interaction with other people is part of the game, your quality as a person, as a member of a community, matters more.