One of the things I don't see mentioned in this thread is the advance of firearm and hunting technology over the last 100 years.
60 years ago, 90% of hunters you'd never seen anywhere near a scope; mostly because of cost both to the scope and to the rifle being good enough to bear it.
Through out the 60's, 70's and 80's you saw massive leaps in numbers that changed over from irons to glass and its only been continuing. Two major driving forces behind this as well; 1. A large portion of shooters today are getting older and finding it harder and harder to use the irons. 2. the cost of glass has been constantly going down, with wider and wider ranges of options for shooters to take advantage of today.
You can also look at the lockers of shooters today and see major changes in quality over the years. Does a great gun make an amazing shooter? No, but it certainly doesn't make him worse.
OP started by talking about hunting at short ranges, which back in the day .30-30 was everyone's best friend and past 100 yards I'm not sure how much I'd trust any of my .30-30's, not to say that the balistics isn't there to say its possible.
Through out the years you saw hunters moving through .30-30 into .308, .270, .30-06 and 7mm phases of "popularity". Every one of those rounds has their pros and cons, but most certainly the POWER of those rounds were driving forces to their popularity.
Not only did calibers change the face of hunting, so did the firearms. At one time, all you needed was a Sears Model Marlin .30-30 and you'd be the epic outdoorsmen. Today, you have post and bedded, light triggers, high magnification scopes, light weight build materials, high standards of quality, and hundreds of other features all coming together in great cocktail of explosive awesomeness.
I do agree with all of OP's sentiments towards making sure its a clean kill, and that one must be sure be ready to ensure the animal does not suffer any longer than it has too. Though I do not know of a single Hunting Instructor that has ever advocated "forget about it suffering, just try to take longer shots."
I will say that one of the greatest things about hunting is the challenge. If I didn't want challenge I honestly would just go to the grocer for all my meaty needs ((and typically that's what happens)). Hunting with my camera has been a real fun addition to the last few years of sitting in the bush. But one of the challenges I do enjoy IS pushing the envelope of range hunting. Currently the record shot sits at 570 yards, with hundreds of rounds down the range to paper to be confident to make that shot from a prone position with rifle rested on pack. To increase that shot to 650 would be a great feeling; but those opportunities just don't come up that often where I hunt.
OP you're going to constantly see a rise in the push for new challenges for hunting; that is simply the nature of the sport/way of life. People thrive on challenge, and as technology continues to improve ((though the last few years Rem has been kinda letting me down there, still have Browning and Savage to enjoy though)) those challenges are just going to continue to evolve.
I do say good on you for wanting to preach great bushmanship in not causing sufferage to the animal; but I will say this "boycott" you suggest simply will do nothing. People will forget about it as soon as the new fangled toy at an "amazing deal" comes along and you just gotta have it.