The big issue with Thunderball stems back to the fact that it was supposed to be the first film made and multiple scripts were written. The original story was created as a film treatment then abandoned. With all this previous work combined with a novel that is rather meandering at times it was perhaps not the film to make after thre massive success of Goldfinger. Here the producers literally were throwing in the kitchen sink and director Terrence Young could only do his best to get the thing finished as they set a hard and rather silly Xmas release date.
Peter Hunt had to somehow cut the 4 hour slow mess into what we have. So it could have been much much worse but here are plenty of Young flourishes to make T worthwhile.