I agree with both of you, but I also think that saying "Kopitar should have more goals" is another way of saying "Kopitar should do more". If Kopitar had 0 goals and 90 assists, that would be wonderful because yes that means that 90 goals were scored however (continuing with they hyperbole), consider two types of assists:
Type A:
Kopitar has the puck on his stick in the neutral zone, passes the puck back to Doughty in the defensive zone as he goes to the bench for a change, Doughty goes end to end and scores.
Type B:
Kopitar picks up the puck in the D zone, rushes up the ice, dekes out a defender and flips a beautiful saucer pass over the last D's stick to a winger for a sweet goal.
Are those two types of assists equal? I think we would all agree the answer is no, and him having 90 type A's would be vastly different than having 90 type B's. Both would be great because someone is scoring, but Kopitar's not doing a whole hell of a lot to make it happen in the type A scenario. A lot of us are frustrated watching him not assert himself in the middle of the ice, only take what he's given, float around the perimeter etc. If he went to the middle more (i.e. "do more" (harder) things), it would result in more assists and goals surely.