I’ve talked about this before in regards to Rogue One, but in general now; with the lack of a huge number of aliens as background soldiers (and I don’t just mean one or two here or there), and basically no aliens in the rebel leadership, across basically all Star Wars media so far, implies very shitty things about the Alliance’s attitude.
Because, given the humanocentric and xenophobic bent of the Empire, the aliens have even more of a reason to fight compared to any given human - but even taking that away, they have at least as much reason to fight, and… we’re not seeing them.
In terms of our universe it’s of course about budget and design and etc etc etc, but, seriously, not even in comics (Vader Down, for example, had a lot of rebel soldiers around, but all/most of those we see are human - and MALE, and in the cut scenes from RotS where the Alliance is being vaguely planned, no aliens. No aliens in the OT, not really any aliens in Rebels beyond the two in the protagonist main cast), and yet again; that implies very shitty things concerning the apparently human-centric “Alliance to Restore the Republic”. The problem is, these aren’t even things we’re really supposed to implicitly assume all things given, and yet they’re there.
If you do not put aliens (especially when you start to have the budget and the space, as Rogue One definitely should have, heck even TFA, as much as I don’t want to touch that) in your goddam rebellion to overthrow a corrupt government and they have at least as much reason, but probably far far more reason than any given human to fight…
We’re going to have to start to assume they’re being excluded, aside from these token bits and bobs of them.
That implies nothing nice.