I'm not sure if I would take this case as the primary and only example of customer service at Marriott. I have run into difficulties in the past (none as bad as the OP) and have had all of my issues resolved to my satisfaction.

OTOH, I have had to dealt with Hilton's customer service for an award stay for someone else, and I was quite aggravated with the level of incompetence of some of Hilton's customer service reps. I was a silver member at that time, and I could not believe that I had to talk every step through to the customer service rep. It seemed like they had no idea what their own internal rules were.