I think the main issue I have with Warriors of the Deep was the way it was lit and directed. The story itself isn't terrible. But you do get to laugh at Myrka, literally a pantomime horse rather than a monster (and played by the guys who were the pantomime horse in Rentaghost).
Ingrid Pitt's terrible martial arts is down to the directing more than the story itself, which I did raise earlier. However, Maddox was no mere work experience guy. Yes he was in training to be the sync operator and had a take over whilst they waited for a replacement; after the fully qualified operator had been killed. But when you're on the sea bed in the middle of the ocean, getting a replacement might prove a little easier said than done, hence why they were using Maddox as the sync operator during training simulations.
But that requires you to cast 3 actors to play the 3 fully trained scan techs - oh dear, too expensive! And then the writer has to think of a ways to kill off all three of them - oh dear, takes a lot of screen time!
So let's just have ONE trained scan tech... and hope the enemy never attacks when he's in the loo, or on a lunch break, or is asleep