No, it could not have been saved, because the writers wrote themselves into a hole from which there was no escape, at least not within the confines of Trek.
Having beamed down to the planet to meet God, one of three things could have happened.
1. They actually meet God. At this point, the entire Trek plotline is basically "over". There's nothing more to accomplish. Obviously, this alternative couldn't have been chosen.
2. They meet some alien. The only possibility that can actually fit within established Trek storytelling. But when the audience is offered the prospect of seeing God, and all they get is an alien-of-the-week, well, that's a let down, even if the SFX had been better than they were.
3. They meet the devil, or at least something that 23rd Century people of faith (such as they were) could interpret as such. The most intriguing possibility, although you'd have to scrap the "action" climax—if you can hurt it with photon torpedoes, it isn't really the devil. But can you really meet the devil in the Star Trek universe? A universe that had negligible discussion of real Earth religion? A universe that had (post-TMP) readopted an accessible, character based style of storytelling (as opposed to the grand, cosmic, epic sci-fi style of films like 2001 or Close Encounters of the Third Kind—a style which could
handle meeting the devil, or God for that matter). I don't think it could have done so.