Know what I mean?
Movie speech is so “elegant”, every word is perfectly spoken.
But reality is like: “um… so you know… I… uh…”… the spur of the moment, non-rehearsed, reality.
Maybe movies should add more “inelegance” to make them seem more “realistic”.
Also there’s the style of delivery - old acting used to be very exaggerated and hammy, then there’s the kind of flawless but somewhat natural style that OP is talking about, through to today’s more realistic “mumbling” style that everyone complains about.
The old hammy style ties back to theatre. Performing live to an audience in seats that can be relatively far takes some degree of exaggeration to seem natural.