I think it's interesting what people consider to be "naturalistic" color representation--the sensitometry and psychovisuals behind why Velvia 50 is considered to have exaggerated colors, while something like Kodachrome 64 is considered to be more natural, is a bit complicated.
Velvia 50 had, among other properties, a higher Dmax (maximum density / deepest black) than other slide films at the time, which allowed it to be shot differently, at a lower EI. Overexposing slides washes out the colors, so this difference alone accounts for some of Velvia's reputation for rich colors.
There were also differences in the sensitizing dyes. These differences are a bit more complicated than what you can capture in an RGB model, so when people try to replicate Velvia's look by increasing the saturation in an image editor, it generally fails. You can't just create an ICC color profile or Instagram filter for Velvia. Other "vivid color" films often tried to achieve more saturation by adjusting the sensitivity curves instead, which creates a very different look from Velvia 50.
People are also used to seeing films which are specifically designed to give a certain look to lighter skin tones. A lot of work went into making people, specifically white people, look "good" in standard consumer films and certain lines of professional films.