Its all about period and asthetic. Sci fi and fantasy art changes over time ,depending on the media. And spaceship design shifts with it ,they go. And they comeback.
And you aren't reading or watching the right stuff. Some of the best starships are now in video games ,I love the "Halo" craft !!!!
I have collected so many books of sci fi art and design over the decades my shelves groan under the sheer weight of them. I've got volumes of work that date back to the past masters of the SF paperback cover like Chris Foss, Jim Burns and Peter Jones. Which is why I loved what they did with "Guardians of the Galaxy", the colour schemes and ship designs are so from that era because they brought Chris Foss back to help with them and I still feel a cold disappointment that the "Dune" concepts he designed for Jadorowsky never came to be, and instead we have had all these adaptions since whose concept designs were truely disappointing.
So I don't agree that with the broader statement that recently all ships are poor. Because CAD has come so far there has been a tendancy towards what I call a more "biological" design, ie craft that have many sleek complex curves and insectoid features that give them a more alien feeling that can now be modelled without the need to physically building them (which would have been impossible decades ago) but its mostly tons better than the bulk of the garbage we had in the 80's and 90's (SW and ST excepted!)
I do think the iconic success with SW OT concepts comes down to just a couple of basic things.
Firstly neither Ralph McQuarrie and Joe Johnston were actually sci fi artists. Ralph, like Syd Mead was a futurist and superb draftsman and designer and both he and Joe and a huge number of the guys from that era were heavily influenced by the designs of WWII aircraft, tanks and militaria, which was the look George Lucas wanted at the time. A war set amoungst the stars but one that looked gritty and real, because he didn't have the budget for anything else.
So they all had an instinctive eye for what look "proper" in the context of the film and for our generation that were raised on war films ( I still enjoy the "Battle of Britian") it was the visual jackpot. And it wasn't just down to the artists ,once the modellers got to work and had time to add that extra dimension of making the concept a physical model that looked proportional and real it gave the ships of that time a unique appeal that has never been bettered to my mind.
But when GL had the money to do what he wanted he went the full "Buck Rogers" ,which moved the SW universe into what I call the sci fi fantasy realm ,rather than that of the practical futurist. So everything became "over the top" elaborations of mirrored and complex spacecraft that made the worlds look perversely less real and less interesting, which upset alot of the core fans (though I still like the Radiant , the tanks and many of the pod racers).
I liked most of what they did with "TFA" . I thought the updated X wings were terrific , I was pleased that they kept the Ties , the SDs and much else ,particularly with what they achieved with the sets and costumes, but I hated the B Brick and the F Frieghter. Looking through the TFA artwork book there was lots in there that was just as unappealling.
The trailer for "Rogue One" REALLY got me excited,simply for what they are bringing back. Of the models at the SWCE I think alot will depend on how they behave on screen. The Tie looks like its wings swivelled up and down, the Walker has a detatchable cargo pod (which rather cooly reminded me of a Space 1999 Eagle Transporter ). The shuttle confuses me a bit, but then the pictures of the front aren't that good.
Personally I'm back to drawing and trying to build designs I did back in my twenties to recapture that star wars feel. I particularly miss the great landcraft like the Sandcrawler, and Jabbas barge, so I'm going for heavy loaders , land barges , and argicultural harvesters plus versions of battlefield craft that are there to fill in a necessary gap between suborbital assault craft and defensive positions.