The constant complaints I hear from rebel players usually fall upon a few of their ships that just fall a little flat.
Several of these ships suffer the same problem, that being a single pilot or upgrade is fantastic but every other build is awful.
I will be running down the list of Rebel ships that most people, myself included, would like to see fixed and why that is problematic for the meta.
The T65 Xwing:
This ship suffers from a lack of positioning actions and a lackluster dial. All its named pilots rock and that keeps it hard to buff the generics as not to flood the meta with wes, porkins, biggs, and wedge. Not to be redundant but the problem lies in Biggs, personally I love his ability and it is fun to work around with tight positioning on either side necessitated, but he is fantastic regardless. Any fix to the T65 also buffs biggs, and biggs won Hoth.
The E wing:
You know where this is going... Corran suffers the same fate as Biggs, being too good for his own ship. E wings are overcosted in general, but any change also buffs another hoth winner. I never see the need to field a knave squadron pilot because its just not worth the points. The E wing is a slightly worse defender in a lot of senses.
The Hwk:
This dual faction ship suffers from being overshadowed by y wings as turret carriers, and the inability for it to function without said turrets by itself. The Azituck will likely overtake it as a higher health crew carrier in the near future. The low health and agility means you can't bring it into support range without risking it, a problem the Azituck will not have and the U wing Does better.
The Y wing:
Why would you ever want to fly a y wing named pilot? Its dial isn't great at all, it takes stress easily. It relies on turrets and Torpedoes. Now TLT y wings are fantastic, but when have you seen a non TLT or stress boat Y wing fielded? Again, This one build setup makes it unappealing to vary loadouts at all. They also tried fixes on it and won't likely spend more time there.
The A wing:
I still think the A wing is a great ship that can be flown in essentially any format and be fun and usually viable, but others disagree. In that light, the A wing has had 2 fixes (Test Pilot and Refit) and a "sort of fix" with snap shot. I think that that ship will only see anything new if it appears in the last jedi, which judging by Mark Hamill sitting in an a-wing is likely.
Star wars is in fact a franchise built to make money. Therefore, why release packs for bad ships that are less iconic if we can make a pack based on the most recent movie. Rebels get screen time so they get the "protagonist expansion packs" and there is no time to release other stuff. Also, if they changed it, we would complain about that.