I agree with someone above who talked about having enough technology to adequately regulate the slow play on the tour, and those identifying the concept of when it is your turn to play, get on with it. For instance, given the game is one of honor where calling penalties on oneself is part of the ethic, each caddie or bag used in competition should have a clock meter of sorts with a control central radio satellite at the course. On the tee, if you are first to play, the caddie or player presses the button, and starts a monitored clock. The device could be as small as the tiniest phone. You then have 45 seconds to play your ball. If there is an outside player controlled agency, like wind blows ball off tee, or spectator that inadvertently walks in LZ, the clock can be stopped. Otherwise, club change, wind gust, etc, can not stop the clock. After each player hits, they are to walk efficiently to the ball, and first to play, sets bag down, pushes button and has 45 seconds. As soon as that player's ball is away, the next to play does the same thing, push button - start 45 second clock. If the player takes more than 45 seconds, a red light comes on, and a radio to the tournament control (which could be a mere computer monitor to record the light 45 second violation. If the player gets (say 3) in a round, they get dinged a stroke. Exceptions can be made for legitimate ball search, O.B., need to go back to tee or penalty drop etc. But, upon addressing the penalty situation, lost ball etc, when it is your turn to play, press the button, start the clock. Failure by caddie or player to engage the button, or play games with circumventing, is automatic penalty called by official on course.
Private play at clubs or public courses are a different matter, also addressed by a few above. There are plenty of legitimate and creative ways for club operators, club pro, committee, or owner- muni overseer, to regulate. I favor the incentive concept, where a total 9 hole or 18 hole time is rated for that course, and a punch ticket is given to the group, with a time punch on first tee to have card punched time stamped upon leaving first tee. They can then punch at a time stamp machine after 9 holes or 18th hole greens, and turn it in for say recovery of a 5-10 time deposit if they meet the time, or forfeit the deposit. Or, a credit in grill room, etc. Also, a proper ranger program to be a 'player assistant' to keep the pace going, and signage "You should reach this tee after 5th hole in X minutes, 9th in X hour and minutes, 18th in X hour, and minutes. You could even put the a couple other time punch machines at 6th tee, 10th tee and 15 tee. Even if the group had fallen behind the course rated benchmark at an intermediate hole along the way, they can take responsibility to make it up with holes remaining. And, the same thing could be applied to local tournaments and outtings.
There are plenty of methods and workable ideas to address this; it only just requires a deeper sense of commitment from the powers that be who are supposed to take care of the game as an institution.