key binding and clicking has absolutely nothing to do with how good or bad you are. this is a fallacy learned from those who have played wow with its multitude of stupid players which nothing would help anyways. with any gcd it is all pointless as to any reaction time PERCIEVED to be saved through key binding. a properly set up hot bar is far better than looking down at the keyboard for which key to hit.
there is no way until you play with someone to tell if they are good or bad. even then it is a matter of opinion with some people. even gear choice isn't always a good indication as what they have now might not be perfect but was better than what they had previously.
what my guild looks for in players for prospective guild members are those that listen and are taught able. if not then we deem them as BAD PLAYERS.