Scrums used to be a lottery really. 2nd row feeds, feet across, not keeping the mark, loose arms, loose heads, collapsing....you name it and they had a penalty for it and refs usually had as many as a dozen infringements to choose from.
And the refs quite often got their calls totally wrong. Going back a few years now but during the 2nd half of the 3rd Origin game of 1982 NSW halfback Steve Mortimer was penalised by Kiwi ref Don Wilson for a 2nd row feed, then marched 10 metres when he protested that it was actually Mark Murray who fed the scrum!!! Ironically out of that referee blunder came Wally Lewis' downfield kick that Phil Sigsworth and Phillip Duke totally stuffed up and allowed Lewis to score the try that ultimately won Qld the series.
I would love to see it made mandatory that ONLY those playing in the forwards can actually pack into a scrum, and that includes when teams are trying to stop the clock. Screw this fullbacks or wingers at lock crap.