Yeah but all those secondary characters you listed have the advantage of having actual personality traits. I'm struggling to remember any of Nexx's dialogue. And you can certainly have cool robot action, but to get the audience to care about the robot action (and by extension the robots themselves), the people inside the robots need to be people you care about.
Change is a funny thing. It jingles around in your pocket while you're walking and you never seem to have enough for the toll booth.
But yeah, the change in Macross II is just not well done.