I still blame golf courses for a large portion of the slow play.
6 minute tee times, thick rough/tall grass/not clearly marked hazards, all add up. If I was a golf course designer that was making a muni for your everyday golfers play, I would NEVER put heather/tall grass on the course. Its absolutely asinine and just bogs down the golf course. At least if you have water out there its an obvious hazard. I cant believe how many courses I have played that have areas that arent marked red that clearly should be (assuming you want to keep a reasonable pace of play). This causes people to look for their ball,etc which takes up considerable time when you have to do it every other hole (depending on the group you are playing with). Combine that with the 6 minute tee times and you are in for 5-6 hour rounds.
Yes golfers do contribute to the slow play as well (I can't stand playing in city tournaments anymore because of the 5.5hr rounds, people grinding over putts/iron shots when they are going to shoot 82 just like everyone else in that day group and we have 0 chance of placing in the top 10 or winning money) but I still believe the golf courses could alleviate a majority of the problems.
If people are hacks there are situations where they really can't speed up if they want to actually post a legit score. Blade balls over a green a few times and its going to make for a slow hole. Also, with hacks, you cant even walk up to your ball to play ready golf, as if you do you will clearly be in harms way of the occasional shank or scull or whatever. You basically have to stand behind them in order to be 100% safe.
I myself am a pretty fast golfer (I can only think of one of my buddies who may be faster, and thats only because he takes 0 practice swings) but this obsession with speed and blaming the golfers needs to kinda stop. Unless you are going to set a handicap limit, or you want people not to post actual scores, the majority of the blame has to fall on the golf courses