The cast time for summoning pets should be an Arcanist thing. The fact you're new to the discipline of Arcane Geometry should mean we have to work to bring forth an entity from our Aether. Once we upgrade to Summoner and Scholar it should be instant cast. We have mastered the basics of being an Arcanist by that point and are now delving more into specialized techniques to control our pets to greater effect. No one is going to trip, fall, and stumble if they lose the cast time on their pet once they hit level 30. Instead the current system where Scholar has to cast for Selene and Eos feels very awkward when Arcanist can do the same instantly but forgets how during the transition to Scholar but not Summoner.