There are many things that can make a movie bad. Lack of talent either in front of or behind the camera, overreaching by the director / producer, a budget totally incapable of bringing the story to life, a stupid story idea to begin with…
Then there are things unconnected with the movie itself that can have an effect.
Producer Gary Kurtz (who had also worked in that role on Star Wars and The Empire Strikes Back) was going through an ugly divorce at the time. The money he spent / lost in the divorce led to a cascade of problems with Slipstream, culminating in the movie never getting a US theatrical release. Which is probably why you haven’t heard of it.