I think we have to be cautious about forming too rigid a view of any actor in his first appearance in any role. It takes a lot of them a little time to get to grips with the character and indeed writers may not always have decided where they're going with that character.
I earlier used the example of Picard coming across as edgier and less confident in Encounter at Fairpoint and I think that Avery Brooks and Kate Mulgrew improved as Sisko and Janeway respectively as time went on.
I don't know if it's true or not but I've heard that in Doctor Who, the producers usually film the first episode in which viewers will see the new actor make his first full appearance out of sequence. That is to say, for example, Matt Smith would have filmed a couple of episodes before filming The Eleventh Hour, his Doctor's first full episode, so as to allow him time to get used to the role and find his feet; the producers know how crucial that first episode is and how much weight viewers will put on it, so they want the actor to be settled in it.
Obviously this couldn't have happened with The Cage or indeed most US tv pilot episodes which, unlike DW, don't have the luxury of knowing that there'll be a full series at the end of it.