JC,
To answer your question, there is nothing wrong with a five-hours round. Five hours equals 300 minutes, which equals less than 20 minutes per hole (20 minutes per hole would be a six hours round.)
I've always laughed at the "old country" folks who claim they play 18 holes in 3 hours. If I play by (not with) myself in the early morning or the early evening, I can make it around in 3 hours.
It's nice that Melvyn goes so far back (hundreds of years, it seems!) that he can tell us what golf was and was not meant to be. I don't mind a little endurance challenge with my golf.
I recall the GW Bush brag during his/their time in office, until he gave up the game, about getting around in Kennebunkport in as brief a period of time as possible. If you are after brief in all your endeavors, then here is a bucket list for you:
--guzzle your next bottle of wine without taking a breath;
--ride a speedy cab through your next tourist destination without stopping for a postcard nor a photo op;
--TIVO your way through every show you've recorded, ignoring the commercials and the program, until you reach the end;
--Read the two cover flaps of your latest book purchase, buy the Cliff notes and skip the original work altogether.
I've little time for the golf snobs who dictate how quickly a round must be completed. I respect your right to voice an opinion in support of 3 hours rounds, but I'll not list it as the sole way to enjoy the game. If you want to play that quickly, find off-hours in which to do it; I and perhaps others won't adhere to such strict guidelines.