It's been 4 whole episode with an introduction of a new set of character, a major villain, several hints toward a deeper plot.
The climatic fight took half an episode and even the flashback didn't last more than a single episode. What part of any of this is dragging it out? This is no where near the coma inducing pace that most other Shounen tend to tell its story.
As far as Ali Baba goes, the only time he has shown true confidence so far is during his sword fight with the guy who own Morgianna. That was because it was a territory he was knowledgeable in, so he has no problem using what he knows. Otherwise, his personality tends to be very hesitant and lack a lot of traits for a real leader. He has no experience leading anyone and lack charisma, he knows this and that is why he is hesitant to take charge.
In fact, this is very consistent with his character. Think back so far and count the number of times Ali Baba took charge without someone else directing him. He only went into the dungeon because of Aladdin power, he only join the fog troupe at Kassim's urging and he only reconcile with Aladdin when he was forced by Morgianna. Like shinta said, Ali Baba is a very flawed character that has plenty of room for growth. If anything, Sinbad presence is making him more hesitant because Sin is such a natural leader.