Honestly there's not much to say about this film that everyone else hasn't already said. It was for a while and arguably still is the most popular and most successful film in history. You can see it. The visuals are stunning from the sweeping wide shots of Tara lit by the Sunset and framing Clark Gable and Viven Leigh against to the most noted shot; the tracking/crane shot that follows Scarlett through the piles of dead bodies in the Atlanta trainyard up to the American flag waving into the frame. The title cards are stunning. The music is soaring and epic. The story is multi-generational and epic. You are literally swept off your feet even before the story begins.
Epics had existed before in film, but not to the degree of production along with color, that this executed. This film sets a standard for Hollywood Gloss and production value that's hard to beat. In the sense of color this film is one of the first to implement color in a somewhat realistic way. The colors are not too distracting from the storyline or the visual composition and production design in general. It is the opposite the color adds a lot to this film in terms of portraying the reality of the South and the reality of the war, paid in blood and soil.
Films have moved into a realm of international effect. It is now more than ever clearly a medium of immense grandeur and artistic and commercial supremacy. Gone with the wind shouts this at the top of the lungs.
This film is a climatic end to the rapid rise in film history that was the 1930’s bringing us from humble beginnings and experiments in film form to a finalized language of film that includes color and sound and major production effects that would be the highest form of filmmaking until CGI comes into play almost 60 years later. Films are shifting back into reality by the end of the 30’s, and they will continue through WW2.
I would say the lasting impact of the film is the fact that a Black woman won an oscar from it and was prevented from attending properly due to segregation laws that existed at the time. The movie gets flak for treating black people as slaves as a thing to glamorize and glorify but at the same time Mammy won an Oscar for her role which was a major achievement for Black people at the time. It's quite controversial in that sense.