If you are photographing living and moving people that is very different indeed to the premise of photographing stationary subjects — how were any of us to know what you were referring to?. If speed, spontaneity and automation is important, use whatever camera you wish for the subject if it needs speed and portability, but one cannot assume it is necessary better than MF or LF in skilled, experienced hands using less automation and refined, paced technique. Remember for decades and decades MF was the only format photographed for weddings, with many beautiful abstract processional movement images created by locals I know of (additional to static portraiture). Weddings have also been shot on pinhole cameras (!).
Probably then, MF and LF is not for those stepping from the comforts of SLRs photographing action to MF and LF, but experimenting with processes and methods in the bigger, more cumbersome and thought-intensive format can be just as educational and foregoing much-loved creature comforts of 35mm.