Courses just need to handle their flows better, properly train marshals and don't be afraid to move a group a hole ahead if they cant keep up or ask them to leave if they fail to.
the problem can be owners are too concerned about $$$ and in many cases unwilling to take strong actions against slower players.
Thankfully my course takes slow play very seriously. Our course is HARD being rated 75.7 and 140. Lots of water( 14 holes) smallish and undulated greens, a few forced carries
We set a time par that is not fast but reasonable and was based on 2 years of analysis. That time par is 4:20 weekdays and 4:30 on weekends. We also invested in a cart tracking GPS system and have walking tags so that every group can be monitored by the proshop on a large screen, starter on laptop and marshal on ipad. Alerts pop up if a group is out of position and the go,fers get a notification on their screen as well as an ongoing colour coded display of their time ( up or down in relation to the time par) ~ 94% of our annual rounds come in at or under and we are one of the busiest courses in the Province averaging about 275 players a day.
We run 10 minute intervals so dont jam groups in although there might be the odd squeeze. We will provide complimentary carts to a group of walkers who simply cannot keep up ( had four 80+ yo walkers this past week that were pacing for 5 hrs until we did)
Its not rocket science ,......but its work
Public golf is public golf and a wise man once told me that if you want to play in 4hrs or less join a private course.
Private courses see less daily volumes, generally have 10-15 minute tee time intervals ( my daughters course is ultra exclusive and runs at 20 mins) and best of all can communicate with members about expectations and problems.
I have not played more than a couple rounds this season but when i do its usually in the first hour and get through in 3-3:15.....unless we get behind a group of walkers out for a stroll