It was long into my life as a movie watcher and professional movie journalist that I finally got around to watching all of Gone With The Wind, finally seeing the lines, characters, motifs and scenes I'd been hearing about for most of my life. And in doing so I was really watchful of two things. One was the differences between movies made in 1939 and now (the 21st century) – from the fashions in staging and performance to the film technology, locations and sets.

The other was the themes I expected to find. I thought I identified several, but the thing about popular entertainment is that if it foments long enough in our consciousness to be recognisable after so long, it's probably gone through so many iterations and interpretations that themes are thrust on it by the visions of a hundred artists who work with it. We've seen it over the last few years with Chris Nolan's Batman, a franchise so weighty with themes and mood it ended up winning an Oscar (albeit for acting). But that's not bad for a story that started out as a guy who fights crime in a cape, even the backstory of his parents being killed by a mugger probably a throwaway idea they came up with in half an hour.

So in Gone With The Wind, I looked for weighty themes like living the end of history, innocence lost, even how the heart's desires drown out what's good for us completely.

In a way it's Civil War mercenary Rhett Butler (Gable) who has a character arc, not spoiled society dame Scarlett O'Hara (Leigh). Even as she learns the truth about hardship and suffering when the war comes to her doorstep and her beloved plantation (Tara) is ransacked to near-rubble, she essentially remains a spoiled brat who's prepared to do anything – even phony marriage – to get what she wants no matter how much trouble she visits on everyone around her.

Rhett is the one (one of the many, in fact) who can't resist her beauty and falls head over heels for her, despite his exterior of rakish charm and self-assurance, effortlessly getting the upper hand with her. But it's the final iconic line of 'frankly my dear, I don't give a damn,' that makes you realise he's the one who's grown up, not Scarlett. Despite how much he wants her, he knows she'll always be a petulant little girl who'll play with his affections whenever it suits her no matter how she feels about him in that moment.

Still, the themes I looked for (and found) might have been illusions. We love themes in literature and movies today because they make us believe we can appreciate art better than anyone else and feel smarter and more educated – it's passé to love something just for the spectacle or story. Because as George Lucas said when an interviewer challenged him on Star Wars' legitimacy because it's 'just science fiction', Gone With The Wind is just a historical soap opera.

It's such a maze of twisting and turning fortunes a rundown of the whole plot would take longer than the reading of it would be worth, but we meet bratty southern belle Scarlett, who's never had to work a day in her life and wants only to marry the dashing Ashley (Howard). When Ashley chooses Scarlett's good-natured cousin Melanie (de Havilland), it sparks off a period of emotional turmoil as damaging as the Civil War drawing ever closer to Atlanta.

Even the presence of handsome smuggler Rhett is only a momentary distraction, and he'll become even more fodder for Scarlett to convince Ashley she's the woman for him. When the O'Hara family has to leave Tara because of the approach of Lincoln's army, everybody is scattered (some killed), and when Scarlett has to be an adult and make it back home while nursing the sick Melanie and evading the northern army, she returns to find the house in ruins.

While she works her fingers to the bone alongside her sister and beloved house maid Mammy (McDaniel), Scarlett vows never to go hungry again in the stirring pre-intermission scene. Rhett, Ashley and many of their contemporaries are changed when they start to return from the war, but it doesn't stop Scarlett picking right up where she left off trying to twist everyone to her will of winning Ashley. Even while she nurses Melanie through sickness, marries Rhett, has a daughter with him they subsequently lose in a horse riding accident, it's still all about her master plan of stealing Ashley for herself.

The four-hour epic has enough breadth to encompass several different styles and moods. The early party scenes have an air of choreographed slapstick, where Scarlett hiding under a bridge in the rain, or her and Melanie shooting a soldier who arrives to loot Tara have the nasty grittiness of films we're much more used to today (even if they're not portrayed with as much gleeful love of violence and suffering).

It was also a time when movies had a different language. With no TV there was no media cross-pollination like we know today when movies are made to be watched anywhere – even on phones. Audiences went to the movies to see spectacle and Fleming (along with other directors who aren't credited) achieved it in several audacious shots like the slow pulling back of the Atlanta streetscape full of injured soldiers.

Of course, you'll see vastly different themes than I will. Just one I've read is about the comeuppance a woman gets for the crime of sexual independence. Instead of being a demure, agreeable, shrinking violet wife for whatever man deigns to have her, Scarlet knows what she wants and fights for it – from the heart of the man she truly loves to economic independence (at various points in the film she runs the cotton farm at Tara and then a lumber business, almost single-handedly) after swearing she'd never again go hungry.

The theory goes that Rhett's final and damning rejection of her is punishment for the scandal of a woman wanting to control her own destiny in an era when women were still little more than chattel. I didn't notice it at the time, but it's there if you do.

Of course one of the most interesting things about the film is the more enlightened social mores we've evolved since the late 1930. The film makes no secret of the fact that Mammy and Tara's other maids, servants and cotton-pickers are slaves, but if the same film were made today there'd be some acknowledgement in the narrative of how wrong slavery was – maybe by having one of them flee, or showing Scarlett's father brutally flogging one for a misdeed.

It might be because Fleming and creative overseer/producer David O Selznick simply considered it a fact of life in the 1860s, but it's more likely that in the 1930s (an era where blacks still had their own bars, public toilets and drinking fountains) neither the studio nor audiences cared.

The other gulf in attitudes that's been commented on is the way Rhett sweeps Scarlett up in his arms, ignoring her protests as he carries her upstairs with a lavish crescendo in the score. Next thing we see her waking up the next morning, stretching contentedly to portray the satisfaction of a night of ardent lovemaking. 70 years ago it was thought the height of a woman's desirability for a man to simply have to carry her to bed and ravish her, but before you even look at all the chatter about the disturbing scene online you'll frown at the gilded, rose-tinted depiction of what appears to be sexual assault.

Politically correct wowsers might cut it out if they had the chance, but however backward the thinking behind the scene was, that's a slippery slope. It's not only a (again, rose-tinted) picture of the era it was depicting, it's old enough to be a document of the art and science of cinema in a very distinctive, long-gone period. The story was about a civilisation gone with the wind, but the phrase could well be talking about the 1930s when stars ere salaried workers and studios reigned supreme.

After all this time, the themes have emerged whether they were intended or not, but without them, it's still one of Hollywood's great grand visions.