If you want to see a rush job on a "cashing-in" attempt at sci-fi, look no further than "Moonraker."
They didn’t use any of the work for the TV show in the movie—look at the photos you posted, those were old costumes, and if you see the pre-production art the sets were completely different from what they used (I think they used the engineering design). Ralph McQuarrie even designed a new Enterprise, but when they went to the movie they went with, I think, Andy Probert as a designer (I know he worked on it, not sure if he was the only designer). When Robert Wise came aboard they basically started from scratch. The script they adapted was being rewritten up until the last days of shooting. Plus they lost tons of time when Robert Abel couldn’t deliver the FX and they had to hire Dykstra and Trumbull (who used Paramount’s time problem to get out of a contract he had with them).
The TV series was dead. When Star Wars was first a hit, they even thought they were lucky to have dropped the idea, since now the SF was over. But when Star Wars was still selling tickets even after Close Encounters came and went in the theaters, they decided it was time.
Some of the rejected scripts—well, the one they used was awful, but I’m not sure how good the others might have been. A couple of the TV scripts were used on Next Generation episodes.