When looking at the majority of classic-space ships/bases, I think their set designs are actually quite good considering the mostly studs-up building style. I think this is especially evident in many of the "neo-classic space" interpretations of the old sets utilizing modern building techniques and pieces. The basic set designs from a play-ability stand point were great.
One thing that modern sets have trouble re-creating is the emphasis on alternate models. All classic sets seemed to be designed such that their parts selection lent well to creating MOCs. This is something where I think modern sets fall short on (with the exception of the creator line). I think there is a trade-off between primary model "coolness" vs part selection variety that enables alternate model building. Today's sets feel closer to "model kits" than a building system.
The other thing that folks look fondly back on classic space was not just a "fad theme" that ran 1 or 2 years. It was a universe or world that enjoyed consistency and longevity. The theme featured a consistent color scheme over a number of years (largely driven by the limited color selection of lego sets in general in the 70s-80s) such that early sets integrated well with the later sets. Also, there were no special collectible mini-figs with a pre-determined backstory... From a kids viewpoint, we created our own stories around the sets built our own creations to fit into those stories and every christmas/birthday my space empire grew. As a kid I was able to collect a number of sets over time and I could use all of those pieces to build my own mocs that fit in with the world/system. As a parent now, one of my frustrations is that the huge variety of colors used in lego themes makes it very difficult to create a "critical mass" of basic and specialty parts for my son to start building his own MOCs without them being "rainbow warriors". For example, we loved the Galaxy Squad sets but we do not have enough of the medium blue color that was used in those sets to use them for any thing but limited trim pieces on mocs. The modern starwars sets are great sets (almost MOC quality) but they also suffer from the color dilution in trying to keep movie-accuracy.
I don't know if the issues I am describing are an out growth of Lego trying to react to the wants/desires of modern children or trying to drive more collector value into their sets.... Some of it is obviously driven by their licensing strategy and trying to create accurate depictions of scenes from Harry Potter, Spiderman, Star Wars, etc
Whether or not Lego decides to resurrect classic space or not, what would be nice is to see inter-theme integration where elements of previous themes are carried forward into the new themes so there is better overlap between the themes. For example, it would have been nice to see some level of color and character integration between Alien conquest and galaxy squad.
I think expecting a full on classic space reboot is a bit much to expect. I am thrilled with Benny's ship in the lego movie and will buy at least two copies (one for me and one for my son). I was hoping we would see the little ship that was seen in one of the Lego Movie posters as a set as well. As I stated in an earlier post, I would be happy with a "classic-space tribute" creator set that featured the classic blue/gray/trans-yellow color scheme and came with a selection of parts to build a spaceship (487 sized) or a land vehicle or a space base. A selection of modern parts and canopies, and PRINTED parts with classic-space emblems and other decorated elements would make me a happy camper as a MOC builder.