6500 is too much yardage for most high handicappers, and 6700 yards is extreme for a 18 handicap. "White tees" need to be down around 6200.
Yeah, tell me about it. My index is 19.5 (or at least it was before yesterday) and for our club championship, nominally played from the "White" tees at 6,270 yards, they had moved a bunch of them back to stretch the course to somewhere in the 6,500-6,600 range.
Then it rained 3+ inches on Saturday so we played 36 holes of stroke play on Sunday with most shots plugging in the fairway. I was completely out of my element with my 185-190 carry distance tee shots. The shortest Par 3 was 151 into the wind and there were several Par 4's where I hit driver and 5-wood and still couldn't reach the green with a wedge. Only a couple of the Par 5's were reachable with driver, 5-wood, 5-wood. Over the 36 holes I didn't hit a single approach shot (in regulation) with an iron. That was the longest 11-1/2 hours I've ever spent on a golf course.
I'd say for the prototypical bogey golfer having "White" or member's tees around 6,200 yards is appropriate on a typical wet/green US course. Conversely, I didn't find playing Deal or Littlestone at 6,400-ish to feel long at all. In fact, I didn't carry a driver for my rounds at Deal opting for hitting it straight with my 3-wood (175 yard typical carry distance).