I remember that back in the day, actors re-voiced what they said on the set, but from a studio with proper recording gear, and sound engineers mixed these voices into the general soundscape.
Are modern movies shot in reporting style instead, with all the visuals and sounds recorded once and simultaneously? That would surprise me.
In some recent musical-to-film adaptations they recorded the voices ON THE SET during filming, often with no backing track or metronome, and then forced the music director, post-filming, to conduct the orchestra along with whatever the hell the actor was filmed doing: https://www.youtube.com/watch?v=1ikqU6G6Xgs
Are modern movies shot in reporting style instead, with all the visuals and sounds recorded once and simultaneously? That would surprise me.