Modern giant monster movies are difficult to make because they have to be both believable and show a spectacle. They are expensive to produce and therefore require blockbuster status at the theaters. It isn't like the golden age where special effects were not expected to look real to enjoy. Some masters of the art didn't need more than clay, lots of time, and patience.
Even when the golden age of monsters in the 50s and 60s was long over, television for a short time gave new life to old celluloid. Late at night or noon after cartoons the giant terrors once again lived. The best of them included insects like a giant tarantula, a flying mantis, and them ants. Forget that no exoskeletal creatures could physically exist. There they were in the theater or on television larger than life and haunting a young kid's imagination. Two of the biggest stars were King Kong and Godzilla. Only once were they together, and that was a disastrous Japanese B movie with more laughs than wonder; no matter what age the viewer.
In later years the giant monsters fell out of favor to be replaced by dinosaurs. The same problems of production values and unbelievability hung on them, but without the supportive audience. It was fine that giant monsters or even insects didn't look real on the screen because they never did exist. Dinosaurs, on the other hand, had proof of their reality. It didn't matter how extinct, they were not lizards with plastered on prosthetics or actors in suites. A few movies with them were made and then died out just as quick.
Late 70s and mid 80s tried to bring back the Great King Kong with limited success. The stories were updated, but movie magic remained questionable. Actors in monster suites had become a joke and stop motion picture animatronics didn't change much either. It seemed that the giant monsters had finally died off in Hollywood.
