If I recall correctly, SR’s production budget got Flyby’s development costs wrapped into it, so the cost is not entirely that production’s fault, but the audience’s lack of enthusiasm sure as hell was!
To this day I still try to imagine what those story meetings were like when they pitched Lois having a kid from the night she had with Superman that she can’t remember, Supes being MIA for the 1st several years of that kid’s childhood, and then returning to be a mopey stalker of his abandoned pseudo-family. Like who heard that at the studio or otherwise and thought, “that’s it! That’s the story we need to bring Superman back to the masses!” Boggles my mind.