Consider the following three rounds, played on consecutive days on the same golf course (Mooresville GC in NC). Fyi, the front 9 at Mooresville is Ross, while the back 9 was added much later. The rough was relatively heavy, and the greens were average or above speed, maybe running 10? There were several holes that were cart path only, but it was mostly 90 degrees. It is a relatively easy course on which to have to search for a ball because there is very high fescue on the borders of many of the holes, and especially on the back 9. One qualifier to this is that the guys in this tournament were pretty good, and I think old guys in general tend to play faster than average. So it wasn't exactly an average group.
Day One, 3 hours and 44 minutes:This was a practice round the day before a tournament (NC Super Senior Championship). Playing as a threesome, hitting a few practice putts to the pin positions for Day 1 and Day 2 of the tournament, which were marked. We did NOT spend a lot of time looking for balls that had gone into the very high fescue on the borders of the holes, and we didn't really "grind" over short putts. The golf course wasn't crowded at all, and I don't think we waited on anybody in front of us even once. Tee times were 12 minutes apart.
Day Two, 4 hours and 21 minutes:This was a tee time fairly late in the times for the first round, with four players. One guy played really well, one guy really struggled, and two of us were just ordinary. I don't think any of the four of us would be considered slow in any respect, and one guy plays FAST. But this was tournament golf; carefullly calculating distances, no "max" score, putting out, looking for potentially lost balls, not using alternate stroke and distance penalties, etc. We could always see the group in front of us, but didn't have to wait, and the group behind us wasn't pushing us. Tee times were 15 minutes apart.
Day Three, 4 hours and 57 minutes:The tournament committee changed the format for the second day to a 10 am shotgun start, due to both the extreme heat and the possibility of afternoon storms. There were 9 holes that had an A and a B group, and we waited on the tee on every hole, and in the fairway on most holes. (Fwiw, Mooresville has 5 par 5's, plus one VERY long par 4, so 9 A and B groups isn't quite as bad as it sounds.) Same situation as Day Two; three players who were at least average in terms of playing fast, and one guy who is way faster than average.
I think there are obvious conclusions to be drawn here; tournament play is slower than casual play for sure; it just takes a long time to grind over a two foot putt that really matters, and to try to find a ball instead of playing the provisional or returning to the tee or previous spot. I play a lot of tournament golf, and honestly anytime I get in under 4:30, I feel like we've played pretty fast.
But the real killer in terms of pace of play is a too-crowded golf course, without a doubt. When courses don't space the tee times enough, or when they allow the next group to tee off as soon as the group ahead of them hits their second shots instead of at the posted tee time, etc, play WILL be slow. This is far more important that anything to do with GCA, or format, or anything EXCEPT individuals who just don't care.