I am not sure if i understand you correctly but with alternating fire and bliz, do you mean doing a couple of fires and then a couple of bliz's? If thats the case i think thats fine, not optimal but surely not a reason to get kicked.

If however you mean literally alternating fire and bliz then thats frankly terrible and not utilizing the class at its base core, which would justify the complaint.
Using fire gives you stacks of a buff called astral fire, which would buff all your following fires by a significant amount. The same happens with casting ice spells but instead they give you a buff called umbral ice, which would give you mp regeneration. Not using that is basically like a melee or tank not using combos.