>>41402857
They did it with two very important things.
1) 35mm film, often Super35. It's analog film with all the granularity that an eye can capture and then some, by the 80s with an accurate colour representation and in the 60s and 70s nowhere near as much. Even then, cameras needed a LOT of light to capture the scene, which sometimes fucked with the colour grading.
2) Processing film and tape was a fully analogue "what it is, it will be" process. They couldn't go into an editor programme and move the colour triangle's delta on a 0.0001 scale with a mouse or a preset in a menu.
Today it's easy to record something that looks real and then fuck with it in post.
Amateur and professional videographers do it all the time.
In modern movies however, they go for a less saturated and high contrast HDR look, which they achieve fully digitally.
Digital CMOS sensor in the camera, digital storage, digital processing, digital rendering, and then shown through a digital IMAX projector that's lower in resolution than the old 35mm stock did for free.