When the reviews come in for each new Trek film, some critic invariably makes the dig that the latest film "feels like a TV episode with a bigger budget." Star Trek III is the only time where that's actually true. There's a lot of individual moments that work in the film, but those moments can't hide the story's true purpose: to reset the franchise back to normal after the events in The Wrath of Khan.
It's hard to remember a time when Trek appealed to a wide base of casual fans - but the original series achieved this with broad characters (there was a Scotsman named Scotty, for God's sake) and self-contained stories. You can jump in at any point in the original series and not feel lost. The same goes for the books and comics that were released steadily during the 80's and early 90's. The Wrath of Khan changed this, with life-changing events for the characters and lingering plot threads. All of these threads are hastily resolved in The Search for Spock so the franchise could return to its standard "tune in next time" mode of operation - which is why The Search for Spock seems so cold and calculated.
This film wasn't made just to resurrect Spock, but also to eliminate the Genesis effect and Kirk's son from the franchise. It's hard to believe that the filmmakers blew up the Enterprise, because it's the only thing stopping the film from having the cast fly off on their next regularly scheduled adventure at its conclusion. True, the resurrection of Spock works well enough. Personally, I can't think of a way to do it better. Where the film fails completely is with David's death and the unstable Genesis planet - the latter making no sense whatsoever.
There are numerous plot holes in The Wrath of Khan (Reliant fails to notice that an entire planet is missing), but the story works so well that you either don't notice or don't care. The Search for Spock's plot holes are so large and so egregious that it's shocking that the movie works at all.
How does Kirk fail to put together that McCoy carries Spock's soul after McCoy breaks into Spock's quarters and speaks in the dead man's voice? If Genesis is now a galactic controversy, why is there one tiny scientific vessel orbiting the planet when there should be an entire peacekeeping force? Why does Kirk hijack the nearly crippled Enterprise, making him a wanted man, when he could buy a small working ship? How does the Federation not go to war with the Klingons after the events in the movie? Most importantly, if the Genesis wave is so unstable that it blows up a planet -- where, mind you, all life on preexisting life would have been destroyed -- like hot dog left too long in the microwave, how does that make it in any way a less effective weapon to those who would use it so?
The answers are simple. Kirk remains oblivious so the exposition can play out. The film's modest budget equals modest special effects. The filmmakers thought they couldn't have a Trek film without the Enterprise (something the next film would disprove). You can't have a happy ending if the better part of the galaxy is at war. And the filmmakers wanted to sweep the Genesis effect under the rug, and they thought killing David, one of its inventors, and making the effect unstable would do it. Harve Bennett's script isn't strong enough to support such obvious plot devices and unbelievable leaps in logic.
It's also a strangely conditional story, nervous about the risks it takes. So what if Kirk blows up the Enterprise? It's going to be decommissioned anyway. All Kirk does is take out the trash. All the new Federation characters are douche bags or officious pricks, so Kirk and company can stuck it to the man. (And why is every Admiral in Star Trek a dick, anyway?) Kirk's son also gets douched up a notch, since he's responsible for the Genesis effect being unstable - which makes his death more of a punishment for his sins. Instead, it robs his death of its proper impact.
Speaking of the Klingons, their actions and motivations are never explained. It's hinted that they're the Klingon equivalent of the Michigan Militia - paranoid men who see everything and everyone as a threat, who are working independently of their government. That could have worked, because something - anything - needed to be added to their section of the story.
The Search for Spock is clearly the work of a first time screenwriter and a first time director, though both men came into their own with Star Trek IV. Any faults in Nimoy's direction don't come from a lack of talent: he's just not suited for much of Star Trek III's material. He has a gift with actors and his camera work is simple, unobtrusive, and effective...letting the story play out with natural ease. The quiet scenes work quite well, but action and adventure are a bit lost on Nimoy. There's nothing wrong with what action there is, but there's not enough of it and what's there is in no way exceptional. The battle between the Enterprise and Klingon Bird of Prey can barely even be called that.
And I don't how much of this has to do with Nimoy, but it's the ugliest Trek film of them all, with terrible costumes, make-up, and production design. Only ILM's effects hold up twenty-five years later. The color pink is all over the place, all the new aliens look downright goofy (even for Trek), and Chekhov looks like Freddy Munster for most of the movie. Normally, I wouldn't knock a movie -- especially an 80's movie -- for this, but it's so awful in places that it's hard to take an otherwise well-made scene seriously.
It's still a pretty decent sci-fi film - better than most give it credit for - but I don't care for its impact on science fiction stories. I was still very young - five or six - when I first saw the film, and the idea of a character coming back from the dead was mind-blowing. It's not the first sci-fi/fantasy story where a character is resurrected, but it became obvious as I grew older that bringing Spock back from the dead was a business decision first and a creative decision second. Maybe I'm too close to this one, but so many sci-fi stories - Trek and non-Trek - have used this same trick so many times now that death rarely feels final. It's especially bad in later Trek stories. When a character dies now in sci-fi/fantasy story, my first thought is almost always "Oh, they'll be back..." Thanks in large part to Star Trek III.