Well I can't argue with any of that except to say my fanboi for the 6.8 ends just past 500 yards. After that I become a 6.5 CM fanboi. And much past 1200'ish I'm totally open to suggestions.
OK, I guess that's reasonable enough to an extent, and I certainly respect knowing the limitations of your equipment.
But why make up all that other stuff about cartridges you know nothing about? You have to know at some level that it makes you look bad and is a detriment to the forum. It just smacks of the classic "Chevy vs Ford" arguments, which really boil down to immaturity and arguing to defend your own choice rather than looking at what's actually best.
Regarding that 500 yard limitation on the 6.8, that's probably about right depending on the load, but I wonder if you're aware that you can basically double that range with either a 6 ARC or 224 Valkyrie? (The trajectory and wind drift are really close between those two with the right bullet and powder choices.) You've commented that you think the AR15 is limited to shorter range, but you're confounding the limitations of your cartridge choice with limitations of the platform.
I own or have owned most of the rounds listed in the OP except the 300 Hamr and 22 Nosler, plus a number of other AR15 rounds that aren't covered here. (With the caveat that my 6mm rifles are an earlier Grendel wildcat rather than the official ARC, but performance and other details are nearly identical other than that .030" shorter shoulder.) Talking about good loads/bullets in each of course, in my experience the 224 V, 6mm, and 6.5mm Grendel are significantly easier to hit with than the 5.56 or 6.8 out past 500-600 yards or so, especially if there are unpredictable winds like when shooting across a canyon. The 6.5 Grendel has a lot of drop to account for, but the 224 and 6mm really stretch out the AR15's capability. My long 6mm in particular feels like cheating at 9000-1,000 yards and beyond, and even the short 12.5" 6mm SBR is easier to hit with in the wind at 600 than my best 16" 5.56.
As for the 6.5 Creed, I like and use that as well, but it's using about 50% more powder, more recoil, and is a fair bit trickier to tune right in a gas gun, and trickier to shoot well in a gas gun too than the small frame stuff. Regardless, if you're trying to make consistent 1,000 yard hits on steel or whatever, there are several good options in the small frame AR15 without needing to step up to the Creedmoor in a large frame or bolt gun.