The Mon Calamari were also treated pretty poorly (although the old EU story of the Empire 'discovering' them was already showing cracks by the time of the prequels, as we see Mon Calamari and Quarren in various places, especially ROTS where they're represented and are the dancers in the opera scene!). The comics in particular show how they became sort of the heart of the Alliance fleet, although Raddus's group were from an earlier rebellion).

Disney's version of the Empire/First Order is a bit more diverse (More female officers, stormtroopers) although they do seem mostly human-centric, at least on the navy/army side (Mas Amedda, for example, remains Palpatine's second-in-command, and it's possible Snoke-or Snoke's original clone host or whatever-was an alien, and of course there's also Thrawn)