How informative is it to use the Old Course during the Open as an example? I think it's an extreme case since you have double greens, cross-overs, long walk backs, usually the largest spectator numbers of any Open and viewing restricted to just one side of each hole.
Isn't it the case that with so many walk backs, the greens on several holes are almost in the line of play for the next hole?
I'm quite sure that those wishing to putt on the 3rd green must wait while players tee off on the 4th hole, and vice versa. There are several examples of this situation on the Old Course, e.g. 1st green/2nd tee; 2nd green/3rd tee; 3rd green/4th tee, etc.
Another issue is the double greens. I recall seeing groups preparing to hole out on the double greens having to wait while the other groups playing a different hole are putting. Perhaps this is not always the case, especially when the holes are cut quite far apart, but I think this is also a major contribution to the long round times.
As a TV viewer, I really don't care so much about long round times. I just want the coverage to focus on players hitting golf shots and exclude the long pre-shot routine and player/caddie discussions. I don't want to see players walking to the tee, lining up putts, weighing up the shot options, deliberating with their caddies, etc. Just show me the golf !!