I like the TOS films for what they are, but I feel that in most cases they really miss the sense of otherworldly adventure that had to have been a major selling point of the series [...]
Am I alone in feeling this?
As an Artist, myself, I definitely understand what you're trying to say, here. In a curious way, having the ca$h to blow on a project takes the fun out of it. If you don't have the budget for a commercial film, you have to go Artsy with it. But ...
Once you've got the budget to go commercial, the urge to be Artsy doesn't go out the window, necessarily ... it's just going the path of least resistance to throw money at a problem. If you can easily afford the life-sized T-Rex robot, then that's what you're going to get. That's when the Artsyness sort of shifts from the obvious to the subtle, because now, it's all in the details. Instead of trying to figure out how to suggest a T-Rex with shadows and keeping things mysterious, you can now present yourself, properly In a way that can be universally understood.
See, I think that's it. Going Artsy is a bit of a risk. You think you're doing good things, but it comes off funny, or weird, or pretentious. When you're after their money, it's not such a bad idea to keep things more-or-less straightforward. I mean, yeah, you budget for ILM, but to get the most bang for the buck, there can't be any ambiguity. It can be a made-up thing, like a Ceti Eel, but it's got to remind people of something living. It can't come off as an Artistic bent, like Disney's "Fantasia" or whatever else, like that ...