I wonder what selective pressures and transitional forms would be found in the transition to "Blue Glowing Thingie"...
Pink-ish/Brown-ish Gassy Thingie?
As for the aliens, SW avoided this problem deftly by... Erm... Eliminating any alien main characters.
Seriously, throughout the movies, only two aliens have been in the main cast. And Chewie couldn't even talk understandably, having his voice composed from animal sounds, while Jar-Jar was so stupid he couldn't represent any species able to make even a simple tool.
As for Star Trek, in the Original Series, most aliens were simple metaphors on political situations. The three exceptions, namely Klingons, Vulcans and Romulans, were given so little screen time they didn't have the chance to develop specific traits. In fact, if you were to characterize the TOS Klingons, you only need two words: "Dictatorial" and "Expansionist", whereas Romulans are "Scheming" and "Xenophobic", and Vulcans a simple human-computer blend (Or maybe well-functioning autists?).
There are only so many tales of random hazard and danger induced by outside influences you can tell, and TOS and TNG have pretty much told them all, several many times over (Misunderstood Alien Lifeform? Innocent Culture Ruled by Malevolent Entity/Machine? Rogue Entity Threatening the Enterprise?), and so, the newer Trek
had to break new ground. And while the success of Voyager and Enterprise could be debated (Though both had plenty of good episodes, like VOY: Muse or Year of Hell, or ENT: In a Mirror Darkly), DS9, with its sweeping, arc-based storyline - paralleling B5, in fact, but taking its story in different directions - actually managed to top all of the preceding Treks, with a few one-off exceptions (TOS: "Mirror, Mirror", "Balance of Terror", "Trouble with Tribbles" and "Enterprise Incident", TNG: "Best of Both Worlds", "Measure of a Man" and probably some others I haven't seen.
They also evolved several cultures in quite subtle ways - the Klingons gained an air of bluster and hiding behind their reputation, to the chagrin of Worf and other traditionalist Klingons, the simmering reforms lurking just beneath the surface of the Ferengi, the Romulan inferiority complex in dealing with the bigger powers, the greatly faceted nature of the Founders, not to mention the no. 1 most complex alien race in all of Trek: The Trills - "humans" who "reincarnate", albeit with a new personality with old traits, and who remember all their old lives along the way.
In fact, the layers of the ST aliens are often ignored because you have to watch a
lot of TNG and DS9 to pick up on them, and even then they usually do not flaunt themselves in your face.