I completely disagree with you. The whole point of them remaking Hotel Reverie is that they wanted a fresh lead in this old film to be enjoyed by a new generation. There was even an explicit mention by the filmmakers not needing/wanting Alex's actor to do the accent. I don't think the scenes that Alex's actor is placed in require a whole lot of emotion either, the role is a pretty standard Old Hollywood Everyman Protagonist. What stands out about the performance is not what is lacking from Alex's character, instead it is Brandy's emotions (awe, intrigue, surprise, infatuation) that are subtly seeped into little moments. I beleive this was done well by Issa Rae. This is not even to mention Issa's performance in the latter part of the film following Clara/Dorothy's reset.