EA studio head in charge of the game, Mike Verdu explained in an email to the press that "the game had fundamental design challenges from the start" and that Tiberium was ultimately canceled due to these flawed design decisions not being able to be corrected.
Poor Tiberium, you weren't loved by all, but you weren't hated by all either. Your trailer piqued our interest, but just couldn't get the job done. As a way of saying goodbye, we embedded your debut trailer after the break. Rest peacefully.