Hi Ed. I am saddened by your continued disappointment. However, I feel that you are really distorting things and can't let your unhappiness go unanswered.
When a family is tested and finds that the men don't match as they were expected to match, that doesn't mean that dna isn't useful for genealogy - it means that the family in question has some work to do to understand why these men don't match as anticipated.
If you are going to advise your friends based on what the vast majority of researchers have found from their use of dna in genealogy, you'll be telling them that it is usually helpful and is often tremendously helpful, while some folks haven't geotten any useful information - yet, and a few folks get information that is a surprise - which they will need to deal with.
In any case, good luck with your research. Terry
ps I see that two of the men who would appear to be a part of your dis-satisfaction have been tested at 25 markers - and have a good number of matches with men of other surnames - men who have been tested at higher levels. If these men (F-3 & F-5) were following the path of folks who are learning the maximum amount from their dna, they would be contacting the close matches to see if the paper trails are overlapping and would also be upgrading to see if these 25 marker matches hold at the higher levels. I anticipate that there is genealogical learning to be gained for these two men.